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IMAT 2015 Answers & Worked Solution | LOCOMOTIVE
IMAT 2015 · Answers & Worked Solution

IMAT 2015 Answers & Worked Solution

All 60 answers, solved and explained — General Knowledge, Logical Reasoning, Biology, Chemistry, Physics & Mathematics. Verified line by line by the LOCOMOTIVE academic team.

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General Knowledge & Logical Reasoning

Current affairs, history, culture, logical and critical-thinking problems · 22 questions
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Although the Earth supports life, it has a mysterious carbon deficit. Compared with other bodies in the solar system the Earth has far less carbon than would be expected for a planet that supports life. Originally it was thought that in the inner region of the dust disc where the Earth formed, temperatures soared high enough for the carbon to boil away. However, observations of developing solar systems have now suggested that the temperature would not have been high enough. It is more likely that fire is to blame. Hot oxygen atoms would have readily combined with carbon, burning to produce carbon dioxide. There would have been fewer of these oxygen atoms further away from the Sun.

Which one of the following, if true, would most strengthen the above argument?

  • AThe carbon that is present on the Earth could have arrived at a later date from an asteroid.
  • BThe abundance of carbon in the asteroid belt surrounding the inner planets increases the further away you get from the Sun.
  • CThere is no theoretical reason why life has to be carbonbased.
  • DThere are other solar systems with Earthlike planets that have an abundance of carbon on them.
  • EAt temperatures that are high enough for carbon to boil away, oxygen would also have boiled away.
Correct answer: B The abundance of carbon in the asteroid belt surrounding the inner planets increases the further away you get from the Sun.

Full explanation

The passage argues that the Earth’s carbon deficit is likely due to carbon being burned by hot oxygen atoms (forming CO₂) in the early inner solar system — rather than carbon boiling away.

Analysis of the given options Option A : This suggests carbon arrived later, but doesn’t directly support the “burning by oxygen” idea.

Option B : This directly supports the argument: it suggests that farther from the Sun (where there would be fewer hot oxygen atoms), carbon is more abundant — which aligns perfectly with the idea that near the Sun, carbon was burned off.

Option C : Irrelevant to the cause of Earth’s carbon deficit.

Option D : Interesting, but it doesn’t support why Earth itself lost its carbon.

Option E : This weakens the old explanation but doesn’t directly support the new oxygen-burning idea.

Summary to learn

Strengthening an argument means adding a new piece of evidence that makes its conclusion more likely to be true, by supporting the specific mechanism the argument relies on — not just any fact that sounds related to the topic. When an argument proposes a specific cause-and-effect chain (for example, “hot oxygen atoms burned away carbon near the Sun”), the strongest support is evidence that the pattern predicted by that mechanism (more oxygen nearby → less carbon; less oxygen further away → more carbon) actually shows up in the real data.

Tom is having a celebration and needs to send out 50 invitation cards. The cards must be at least 6 cm wide and at least 8 cm high and Tom wants to put a photo on the card. Each type of card has a standard version and a deluxe version. The prices (per card) that have been quoted to Tom are shown in the table below:

IMAT 2015 question 2 figure
Tom wants to buy the cheapest type of card possible but is willing to pay for the deluxe version instead of the standard.

What is the total extra that Tom would have to pay to buy the deluxe cards?

  • A€30.00
  • B€20.00
  • C€25.00
  • D€22.50
  • E€27.50
Correct answer: D €22.50

Full explanation

According to the limitations of the invitation cards, we can exclude 1st, 2nd, and 4th types of cards. Among the rest of the cards, the cheapest option for 50 cards in the deluxe version is €97.5 (50 x 1.95). For standard — €75.

Thus, the total extra that Tom would have to pay for the deluxe cards is 22.5 (97.5 – 75).

Summary to learn

“Cheapest option that still meets the requirements” problems are solved in two separate steps: first apply every stated constraint to eliminate any option that fails to qualify at all, and only then compare prices among the options that are still eligible. Skipping the elimination step and comparing all prices directly can make a disqualified option look like the cheapest choice when it was never actually available.

Now, it might be thought an amazing coincidence if Earth were the only planet in the galaxy on which intelligent life evolved. If it happened here, the one planet we have studied closely, surely one would expect it to have happened on a lot of other planets in the galaxy — planets we have not yet had the chance to examine. This objection, however, rests on a fallacy: it overlooks what is known as an ‘observation selection effect’, so it wouldn’t be such a coincidence. Whether intelligent life is common or rare, every observer is guaranteed to originate from a place where intelligent life did, in fact, arise. Since only the successes give rise to observers who can wonder about their existence, it would be a mistake to regard our planet as a randomly selected sample from all planets.

Which one of the following best expresses the main conclusion of the above argument?

  • AOur planet is not a randomly selected sample from all planets.
  • BHowever common intelligent life is, every observer will certainly originate from a place where intelligent life did, in fact, arise.
  • CIf life had evolved here on Earth, it would probably have happened on a lot of other planets in the galaxy.
  • DThere would be no amazing coincidence if we discovered that Earth were the only planet in the galaxy on which intelligent life evolved.
  • EIt would be an amazing coincidence if Earth were the only planet in the galaxy on which intelligent life evolved.
Correct answer: D There would be no amazing coincidence if we discovered that Earth were the only planet in the galaxy on which intelligent life evolved.

Full explanation

It addresses the idea that it would seem like an amazing coincidence if Earth were the only planet with intelligent life. But — it says this thinking is flawed because of an observation selection effect. So, it wouldn’t actually be a surprising coincidence.

Analysis of the given options

Option A : True, but it’s a supporting point, not the main conclusion.

Option B : Also true, and central to the reasoning, but this is a premise leading to the conclusion.

Option C : That’s the belief the passage is arguing against.

Option D : This captures the passage’s point exactly — it directly addresses the initial claim about coincidence and says there’s no amazing coincidence because of the observation selection effect.

Option E : This is the initial claim being challenged.

Summary to learn

An argument’s main conclusion is the single overall claim that every other sentence exists to support or explain — it is usually the point being defended, not a supporting reason, and not the opposing view being argued against. A sentence that merely restates the objection the author is refuting, or that states one premise used along the way, is not the conclusion even if it appears prominently in the passage.

Alberto has decided to paint his dining room. Paint comes in 1 litre cans. The paint in one can will cover an area of approximately 24 square metres. The dining room is 4 m x 6 m x 3.5 m high. There is just one window which is in one of the long walls and is 1.5 m x 2 m.

All of the walls, door and ceiling are to be painted with the same type of paint.

Approximately 20% of the wall area to be painted is wood which will need a second coat of paint.

What is the minimum number of cans of paint that Alberto should buy to have sufficient to complete the room?

  • A4 cans
  • B6 cans
  • C5 cans
  • D2 cans
  • E3 cans
Correct answer: C 5 cans

Full explanation

– Painting the room –

Room measurement — 4 m x 6 m x 3.5 m high

Side walls area — 2(6m x 3.5m) = 42 m2

Front and back wall areas — 2 (4m x 3.5m) = 28 m2

Ceiling area — 6m x 4m = 24 m2

Since, 20% of the wall area need second coat,

Total wall area to be painted = 120% ((42 m2 + 28 m2 – 3m2 (window))

= (120)/(100) × 67 m2 = 80,4 m2

Total area to be painted = 80,4 m2 + 24 m2 = 104.4 m2

Since 1 can of paint can cover an area of approximately 24 square metres, for 104.4 m2, 5 minimum cans of paint are required.

Summary to learn

Multi-stage area or volume problems (like painting a room) are solved by breaking the shape into its separate surfaces — walls, ceiling, floor — calculating each area on its own, then combining them according to the problem’s own rules (subtracting openings such as windows and doors, and adding extra coats where stated as a percentage) before converting the total into a number of discrete units, such as tins or cans, always rounding up since a partial can still needs to be bought in full.

Children are being encouraged to take up gardening through special events at shows and activities in schools. It is hoped that an interest in gardening, and particularly growing one’s own food, will make children more interested in learning about their food and they will therefore be deterred from eating junk food. The initiative should be supported and spread to more schools as quickly as possible.

Which one of the following, if true, would most weaken the above argument?

  • AThe practical experience of gardening is not a traditional academic subject.
  • BThe events to encourage children to garden also included stands where junk food was for sale.
  • CSome schools do not have a garden.
  • DIt tends to be older people who are interested in gardening and growing their own food.
  • EMost children have enjoyed the events provided, but have not gained an interest in gardening itself.
Correct answer: E Most children have enjoyed the events provided, but have not gained an interest in gardening itself.

Full explanation

The argument is saying that — Children are encouraged to garden through school activities. It’s hoped this will make them care more about their food and deter them from eating junk food. Because of this, the author argues the initiative should be supported and expanded.

A statement showing that the gardening events don’t actually lead to an interest in gardening, or that the link between gardening and reduced junk food consumption doesn’t hold, would weaken this argument.

Analysis of the given options Option A : Irrelevant to whether it helps children avoid junk food.

Option B : Ironical, but unless it says kids bought junk food or it reduced gardening interest, it doesn’t directly weaken the argument.

Option C : This limits where the program can run but doesn’t challenge whether the idea works where it’s tried.

Option D : Demographic info about adults — doesn’t directly weaken the claim about children’s response.

Option E : The whole initiative’s goal is to get kids interested in gardening so they care more about their food. If most kids enjoy the events but don’t become interested in gardening, the expected outcome (better food choices, avoiding junk food) is unlikely.So, this effectively weaken the argument.

Summary to learn

An argument that predicts an outcome from an initiative (“doing X will cause result Y”) is weakened most directly by evidence that the initiative fails at the very link connecting X to Y — for example, showing that people engage with the initiative itself (X) without ever developing the follow-on interest or behaviour (the necessary step toward Y). This is a stronger weakener than facts about who is affected or how available the initiative is, since those don’t address whether the causal link actually holds.

Leroy cycles to work each morning. The first half of his journey is uphill and he can manage only a steady 5 kilometres per hour. The second half, however, is downhill and he covers this at 15 kilometres per hour.

Which one of these graphs could show Leroy’s journey?

  • A
    IMAT 2015 question 6 answer option A
  • B
    IMAT 2015 question 6 answer option B
  • C
    IMAT 2015 question 6 answer option C
  • D
    IMAT 2015 question 6 answer option D
  • E
    IMAT 2015 question 6 answer option E
Correct answer: E

Full explanation

The graphs in the options given are distance-time graphs. So, the slope of this graph tells the velocity or the rate of cycling. Steeper the line, greater is the velocity.

Leroy divides the journey into the first half and second half. So, there will be 2 sections which have equal distance. From this information, we can exclude the graph B (first half has shorter distance than second half).

The journey is from home to work, so, the total distance should cover some distance, but not zero surely. So, we can exclude the graph C and D.

Rate for the first half = 5 kilometres per hour Rate for the second half = 15 kilometres per hour Second half has seen higher velocity — a steeper graph line.

Therefore, graph E is the most appropriate one for the journey.

Summary to learn

On a distance-time graph, the steepness (slope) of the line represents speed — a steeper line means a faster speed, a horizontal line means the object is stationary, and the graph should start and end at values matching the actual start and end points of the journey. A journey with two unequal-speed halves covering equal distances is shown by two straight segments of equal horizontal length but different slopes, with the faster half drawn steeper.

Studies are taking place to assess the benefits to dental health of adding fluoride to drinking water, a process known as mass medication. The Health Minister has urged consideration of fluoridation, particularly in deprived areas where dental care is poor. Fluoride can occur naturally in the water because of fluoride containing minerals. Fluoride, if in the water, improves dental health by up to 50 percent. Even so, fluoridation should not take place. A campaign leader opposed to fluoridation has spoken of her experiences of living in a fluoridated area of the USA. She experienced feelings of apathy and depression; her 2 year old son showed autistic tendencies and had white flecks on his teeth. These symptoms disappeared when they returned home from the USA.

Which one of the following is an underlying assumption of the argument above?

  • AMass medication is always wrong.
  • BFluoridation of water is a person’s only source of fluoride.
  • CThe reported health symptoms were caused by fluoride in the water.
  • DFluoridation is cheaper than improving dental facilities.
  • EFluoridation is only necessary in deprived areas.
Correct answer: C The reported health symptoms were caused by fluoride in the water.

Full explanation

The passage mentions fluoride improves dental health.

The Health Minister supports its use in areas with poor dental care.

But — a campaign leader argues against it, citing personal health issues and those of her child while living in a fluoridated area, which disappeared when they left.

Conclusion: Even so, fluoridation should not take place.

We need to find an assumption which is something the argument depends on being true for the reasoning to make sense, even if it isn’t stated directly.

Analysis of the given options Option A : No — the argument doesn’t claim this, it focuses on the specific case of fluoridation.

Option B : Irrelevant to the argument’s reasoning about health effects in fluoridated areas.

Option C : Yes — this is crucial. The campaign leader blames fluoride for her and her son’s symptoms, and uses this as a reason against fluoridation. If those symptoms weren’t caused by fluoride, the argument falls apart.

Option D : This is never discussed or implied.

Option E : Also not assumed. The campaign leader opposes fluoridation altogether, not just in deprived areas.

Summary to learn

An underlying assumption is a claim the argument’s conclusion needs to be true even though it is never stated outright — not a claim actively argued for in the passage, and not a background fact that could be true without affecting the conclusion. The negation test is the reliable way to check: assume the candidate statement is false, and if that makes the argument’s own reasoning collapse, it was a required assumption; if the conclusion could still stand, it wasn’t.

Concern about the effects of chemicals upon the environment has led to calls for more research. But we should not wait for further research before we ban some of the chemicals used by industry. If anyone has a good reason to think something is harmful, it should not be used until, or unless, the risk is found to be zero. We know enough about past mistakes to be forewarned. Much of the harm to wildlife and humans is longterm, and the disturbing results we see today reflect the chemical environment 40 years ago. Thousands more chemicals have been released into the environment since then.

Which one of the following most closely matches the reasoning above?

  • APeople should not be able to adopt children until proper checks have been carried out. Serious consequences may follow if adoptive parents are unsuitable.
  • BA suspected terrorist should be arrested at once. Waiting for conclusive evidence in the past has resulted in atrocities that could have been avoided by acting on suspicion, and the threat of terrorism has grown.
  • CSome homes for the elderly have been found to give dangerously substandard care. Therefore they should be closed down and the residents found acceptable alternatives.
  • DCyclists should not place too much confidence in the benefits of helmets, because there is no conclusive evidence as yet that helmets prevent serious injuries.
  • ESome cars that have passed the annual roadworthiness test would not pass 6 months later. Cars should be tested more than once a year once they pass a certain age.
Correct answer: B A suspected terrorist should be arrested at once. Waiting for conclusive evidence in the past has resulted in atrocities that could have been avoided by acting on suspicion, and the threat of terrorism has grown.

Full explanation

Core reasoning pattern:

If something is suspected to be harmful based on reasonable grounds, it should be stopped immediately without waiting for full proof, because past delays have caused damage, and risks continue to grow.

Analysis of the given options Option A : This is about taking precautions before acting — but it’s about prevention before action rather than halting suspected harm before full proof.

Option B : Yes — this is a direct match. It argues for acting on suspicion without waiting for conclusive evidence, citing past inaction that led to serious consequences and a growing risk.

Option C : This is about confirmed cases of harm, not acting on suspicion.

Option D : This is about being cautious in assuming benefit without proof — not about stopping a suspected harm immediately.

Option E : This suggests increasing vigilance, not halting something suspected of harm before conclusive proof.

Summary to learn

Matching an argument’s abstract reasoning pattern across different topics means identifying its logical shape — here, “a credible suspicion of serious harm justifies acting immediately, without waiting for full proof, because delay has caused damage before and the risk keeps growing” — and then finding which unrelated scenario reproduces every one of those same structural pieces (suspicion-based action, no waiting for proof, past cost of delay, a growing risk), rather than picking an option merely because it shares the original’s general subject area or its conclusion’s tone.

When I made a hotel reservation online yesterday I was given an 8 digit

booking reference which contained no zeros. It did, however, consist of three 2 digit odd numbers followed by the sum of these three numbers, and all eight digits were different.

The first digit of the booking reference was 4. What was the last digit?

  • A3
  • B5
  • C9
  • D7
  • E1
Correct answer: D 7

Full explanation

Given info about booking reference code

– 8 digits

– No Zeros

– three 2 digit odd numbers followed by the sum of these three numbers

– all eight digits were different.

– 1st digit is 4

Possible last digit – ?

As far as we know, the digit is 4 O X O X O \_ \_ (O = odd number)

Since the last 2 digits are the sum of the former three 2 digits, we will try to make these three former digits the smallest number possible.

4 O X O X O \_ \_

In places of O, 5 odd numbers are available — 1, 3, 5, 7, 9

Even numbers available — 2, 6, 8

If we think of the first three 2 digits without odd numbers and using the smallest number possible from even numbers — 40 + 20 + 60 = 120 (already overshoot the 2 digit limit). So, we need to take a number from the odd numbers. We will take the smallest first — which is 1.

So, 40 + 10 + 20 = 70 (seems to work, so, let’s continue thinking of odd numbers — 3, 5, 7 and 9 are left.)

Let’s put the smallest odd numbers first.

43 + 15 + 27 = 85 (5 repeats – so, do not work)

43 + 15 + 29 = 87 (Perfect! — no numbers repeat)

Booking reference code – 43152987

So, the last digit is 7.

Summary to learn

Number puzzles with several linked constraints (a fixed digit count, no repeated digits, one part of the number equal to the sum of other parts) are best solved by testing the smallest possible values first for the free digits, since minimizing them typically finds a working solution fastest, then checking that solution against every stated constraint (no zeros, no repeated digits) before accepting it.

Climate scientists in Greenland studying patterns of plant growth have suggested that the early arrival of spring in the Arctic threatens to drive down populations of migrating animals such as caribou. However, comparable studies elsewhere show that their fears are unfounded. A recent study of great tits in Oxfordshire showed the birds are capable of adapting to climate change better than many scientists expected. Over the past half century, the birds have brought forward the date they lay their eggs by two weeks, so that young are born when plant eating grubs are most plentiful.

Which one of the following is an underlying assumption of the above argument?

  • AMigrating animals in the Arctic can adapt to climate change as successfully as great tits in Oxfordshire.
  • BBirds are more adaptable than large mammals such as caribou.
  • CUnless animals like the caribou produce their young earlier in the year, their population will fall.
  • DThe scientists working in Oxfordshire have greater expertise than those working in Greenland.
  • EClimate change in Greenland and climate change in Oxfordshire are of the same scale.
Correct answer: A Migrating animals in the Arctic can adapt to climate change as successfully as great tits in Oxfordshire.

Full explanation

The implied conclusion from the given paragraph is that The fears that earlier springs in the Arctic will harm migrating animals like caribou are unfounded (or at least possibly overstated). Because evidence from elsewhere (Oxfordshire’s great tits) shows species adapting successfully to climate change.

To make this argument work, there’s an unstated assumption: that migrating animals like caribou can adapt in a way similar to the great tits.

Analysis of the given options Option A : This is the correct answer. The argument’s comparison only makes sense if we assume that Arctic animals are capable of adapting in the same way. Without this, the Oxfordshire study wouldn’t weaken concerns about Arctic animals.

Option B : This would actually weaken the argument’s reasoning, because if birds are more adaptable, then you can’t safely assume caribou would manage the same way.

Option C : This statement highlights the problem, but it’s not an assumption supporting the counter-argument about adaptability.

Option D : The argument isn’t about which scientists are more expert — it’s about the adaptability of species in response to climate change.

Option E : While this might seem relevant, the argument’s core reasoning hinges on biological adaptability, not whether the environmental changes are equally intense.

Summary to learn

An underlying assumption is a claim the argument’s conclusion needs in order to hold, even though the passage never states it — not a fact that would actually undercut the reasoning, and not a side observation unrelated to why the conclusion follows. Here, applying an example from one type of organism (birds) to a conclusion about a different type of organism (large migrating mammals) only works if there is an unstated assumption that the two groups are comparably capable of adapting.

The table below shows the average mass of the cerebellum, which is a part of the brain, and total body mass, for a number of animal species. The cerebellum of a cat has an average mass of 5.3 g, while a cat’s average body mass is 3.5 kg.

IMAT 2015 question 11 figure
For which of the species shown is the ratio of cerebellum to total body mass closest to that of the cat?

  • APigeon
  • BSquirrel
  • CDog
  • DRabbit
  • EMouse
Correct answer: E Mouse

Full explanation

Work out each species’ ratio of cerebellum mass to total body mass, in the same units (grams) throughout so the ratios can be compared directly. The cat’s body mass is given as 3.5 kg in the question, which converts to 3500 g.

Cat:5.3 g3500 g= 1.514 × 10−3

Mouse:0.09 g58 g= 1.552 × 10−3

Pigeon:0.4 g500 g= 0.800 × 10−3

Squirrel:1.5 g350 g= 4.286 × 10−3

Rabbit:1.9 g1800 g= 1.056 × 10−3

Dog:6.0 g3500 g= 1.714 × 10−3

The cat’s own ratio is 1.514 × 10−3. The pigeon (0.800) and squirrel (4.286) are immediately far off this value, and can be excluded straight away. That leaves three closer candidates to compare directly against the cat:

Rabbit: |1.514 − 1.056| = 0.458 × 10−3 away.

Dog: |1.714 − 1.514| = 0.200 × 10−3 away.

Mouse: |1.552 − 1.514| = 0.038 × 10−3 away.

The mouse’s ratio is by far the closest to the cat’s, so the mouse has the closest cerebellum-to-body-mass ratio to that of the cat.

Summary to learn

Comparing ratios across very different scales (like a tiny animal and a large one) is easiest done by writing each ratio in the same standardized form, such as ×10⁻³, so the numeric parts can be compared directly against each other rather than trying to compare raw fractions with wildly different denominators.

Sports are played either as a means of getting exercise or as a competition with an opponent. Some sports, such as football, involve a large amount of running and some people are more motivated to run when it is part of a game. Other sports, such as pool, do not involve much physical activity and so it is unlikely that they would be played for the exercise.

Which one of the following conclusions is best supported by the passage above?

  • AFootball is a better sporting activity than pool.
  • BThere is no point in running as a hobby, since football is more fun.
  • CIt is easier to exercise when it is as part of another activity, such as playing sport.
  • DPeople who play pool are more likely to be interested in the competition than those who play football.
  • ESince the main reason for playing sports is to get exercise, pool should not be classified as a sport.
Correct answer: D People who play pool are more likely to be interested in the competition than those who play football

Full explanation

Main idea of the passage

Sports are played either for exercise or competition.

Some sports (e.g., football) involve a lot of exercise.

Some sports (e.g., pool) involve little physical activity and so, unlikely to be played as an exercise.

So, the author wants to specify two categories of purposes to do sports : exercise and competition.

Analysis of the given options Option A : It is not stated in the passage.

Option B : Passage never says running is pointless; also no direct comparison of “fun” levels.

Option C : This is provided as a fact to support the main idea. Not the main conclusion.

Option D : Correct. This is a fact that can be concluded from the given paragraph. 2 categories : exercise and competition.

Option E : Passage never claims the main reason for sports is exercise; it clearly mentions both exercise and competition as valid reasons.

Summary to learn

The strongest supported conclusion from a passage is the one that follows logically from everything stated, without requiring extra assumptions the passage doesn’t actually make. When a passage sets out two separate categories explaining a behaviour (here: playing sport for exercise, or playing sport for competition) and then notes that one specific activity fits poorly into the first category, the safest inference is that instances of that activity are relatively more associated with the remaining category — not a sweeping claim about which activity is objectively “better” or an absolute rule about every participant’s motive.

Looking in his rear-view mirror, Graham sensed that there was something wrong with the number plate of the car behind him. When the car overtook him and he saw its rear plate he realised that the front plate had been upside down.

IMAT 2015 question 13 figure
What had Graham seen in his rearview mirror?

  • A
    IMAT 2015 question 13 answer option A
  • B
    IMAT 2015 question 13 answer option B
  • C
    IMAT 2015 question 13 answer option C
  • D
    IMAT 2015 question 13 answer option D
  • E
    IMAT 2015 question 13 answer option E
Correct answer: D

Full explanation

IMAT 2015 question 13 figure

The correct number plate : S308 CNH

First, we can exclude some options.

Exclude option A and C because S and 3 should be facing each other.

Exclude option E because the larger curvature of S should be facing outwards.

Exclude option B because C should be facing N.

So, the only option left is option D.

Summary to learn

License-plate and orientation puzzles are solved by tracking exactly how each individual feature of an object — the direction letters and digits face, which way any asymmetric shape’s curve points, which characters sit adjacent to which — changes under mirroring (as in a rear-view mirror) and under a 180° rotation (as when a plate is fitted upside down), then eliminating any option that gets even one of those features wrong.

Although it is sometimes suggested that the congestion caused by the bunching of cars on motorways could be eased by increasing the speed limit to 150 km/hr, such an increase would not be a good thing. An estimated 35 per cent of drivers exceed the speed limit by 20 km/hr and would continue to do so if the limit were raised. Since bunching is caused by speeding drivers trying to pass those who observe the speed limit, raising the limit to 150 km/hr would result in the same amount of congestion, but at an increased speed. Moreover, a higher speed limit would encourage all drivers to drive faster, and thus would increase the existing danger from those who drive too close to the car in front.

Which one of the following best expresses the main conclusion of the above argument?

  • ACongestion on motorways is caused by speeding drivers trying to pass those who observe the speed limit.
  • BA higher speed limit on motorways would encourage all drivers to drive faster.
  • CAn increase in the speed limit would increase the existing danger from those drivers who drive too close.
  • DRaising the speed limit to 150 km/hr would not reduce congestion on motorways.
  • EIt would not be a good thing to increase the speed limit to 150 km/hr.
Correct answer: E It would not be a good thing to increase the speed limit to 150 km/hr.

Full explanation

Some people suggest raising the speed limit to 150 km/h to reduce congestion. This is antagonized by several facts. So, the conclusion leads to the fact that the suggestion would not be a good thing.

Analysis of the given options Option A : This is a supporting fact, not the overall conclusion.

Option B : Another supporting point, but not the overall claim.

Option C : Again, a supporting reason, not the main argument.

Option D : Partially true, but only covers congestion, while the argument also discusses safety concerns — too narrow to be the main conclusion.

Option E : Exactly matches the final judgment made after presenting all the facts.

Summary to learn

The main conclusion of an argument is the overall judgement everything else in the passage is offered to support — here, a final “this would/would not be a good idea” verdict reached only after several separate supporting reasons (each addressing one specific consequence) have been laid out. A sentence describing just one of those consequences is a premise supporting the conclusion, not the conclusion itself, even when it appears in a similar position within the passage.

Food producers are resisting pressure to reduce still further the levels of salt in food. Although it is proven that salt intake must be reduced by those with hypertension, there is no evidence that reducing salt intake prevents hypertension. So why should we all be deprived of the pleasures of salt in food? We certainly need to identify those with hypertension and give them advice on their salt intake, but why should everyone else be deprived of salt? Food producers are right to resist the pressure.

Which one of the following best illustrates the principle underlying the argument above?

  • AAdding fluoride to drinking water has reduced tooth decay, but fluoride is unwelcome to some people. Instead, dentists should advise patients with tooth problems on better tooth care.
  • BThe requirement to wear seatbelts has reduced deaths in car accidents but was unpopular when first introduced. People eventually accepted such changes even if it has not benefited them personally.
  • CAdvice to wear sunblock to protect the skin from harmful rays is ignored by some people. Those people should be charged for medical treatment for skin cancer.
  • DPassive smoking is still a problem for people who share a home with a smoker. The law should be extended to make smoking illegal even in the home.
  • ERetailers cannot sell alcohol to people under 18 years, but providing more general advice on alcohol in schools would be better, as it would encourage young people to be self limiting in their consumption of alcohol.
Correct answer: A Adding fluoride to drinking water has reduced tooth decay, but fluoride is unwelcome to some people. Instead, dentists should advise patients with tooth problems on better tooth care.

Full explanation

The underlying principle is: Target the advice or restriction to the group who needs it, rather than applying it unnecessarily to everyone.

Analysis of the given options Option A : Matches perfectly: Don’t impose a general measure (fluoride for all); target individuals with problems. Same principle as salt and hypertension.

Option B : This supports general measures for everyone — opposite to the argument about not imposing on everyone.

Option C : This discusses punishment for non-compliance, not about targeting advice or avoiding general restrictions.

Option D : This promotes even stricter general rules — again, opposite to the principle about only targeting those necessary.

Option E : Talks about education, not about avoiding unnecessary restrictions.

Summary to learn

Identifying an argument’s underlying principle means stripping away its specific subject matter to state the general rule being applied — here, “target advice or restriction only at the specific group that actually needs it, rather than imposing it on everyone.” A different scenario “illustrates” the same principle only when it reproduces that same general structure (a targeted response to a subgroup’s specific problem) with a completely different topic, not when it merely discusses a related public-health issue.

There are two services between Sandpoint and Genville: a fast hovercraft service which takes 50 minutes and a slow ferry which takes 1 hour 40 minutes. They both stop in port for 20 minutes at each end before starting the return journey. They start out from Sandpoint together at the same time each morning.

For how long has the slow ferry been sailing before it meets the hovercraft coming back? (Answer to the nearest minute if necessary.)

  • A1 hour and 20 minutes
  • B1 hour and 7 minutes
  • C1 hour and 30 minutes
  • D1 hour and 25 minutes
  • E1 hour and 10 minutes
Correct answer: A 1 hour and 20 minutes

Full explanation

Trip from Sandpoint to Genville

Fast ferry — takes 50 minutes

Slow ferry — takes 100 minutes

When they arrive at port, stop for 20 minutes and then return.

Question : For how long has the slow ferry been sailing before it meets the hovercraft coming back?

When the fast ferry finishes its route from S to G and starts the return journey, 70 minutes pass and the slow ferry is more than half way.

Assume the total distance = D Fast ferry speed = D / 50 minutes.

Slow ferry speed = D / 100 minutes.

Suppose they meet t minutes after the hovercraft leaves Genville (after 70 minutes).

In those t minutes: – Fast ferry travels: (D/50) × t distance back towards Sandpoint.

– Slow ferry travels: (D/100) × (70 + t) distance towards Genville.

Since they meet when the sum of the distances they have covered is equal to D:

Distance traveled by ferry + Distance traveled by hovercraft = D

(D)/(100) × (70 + t) + (D)/(50) × t = D

(70 + t)/(100) + (t)/(50 ) = 1

70 + t + 2t = 100

3t = 30

t = 10 minutes

So, total sailing time = 70 + 10 = 80 minutes (1 hour and 20 minutes)

Summary to learn

Meeting problems with two vehicles starting together, travelling at different speeds, turning back at fixed endpoints, and pausing at each end are solved by tracking each vehicle’s position as a function of elapsed time (using distance = speed × time, or equivalently working in fractions of the whole route completed per unit time), writing an equation for the moment their positions coincide again, and solving for the unknown time.

A farmer wishes to fix fencing rails to posts which are already in place. The posts are shown in the diagram. The farmer has a supply of rails, each one 2.4 m long. One rail or part of a rail is to be fixed between each pair of posts. (He can cut the rails into smaller lengths.)

IMAT 2015 question 17 figure
What is the smallest number of rails that he could use?

  • A5
  • B3
  • C4
  • D6
  • E7
Correct answer: A 5

Full explanation

Read the seven gaps straight off the diagram: 115, 90, 120, 180, 210, 150 and 210 cm between the eight posts. Because the fencing has to run unbroken from post to post with no joins, each gap needs its own single piece of rail – whole or cut – so the total length of rail actually used is just the sum of the gaps: 115 + 90 + 120 + 180 + 210 + 150 + 210 = 1075 cm.

Each rail is 240 cm long. Four rails give at most 4 × 240 = 960 cm of usable length between them – already short of the 1075 cm needed, no matter how cleverly they are cut. So four rails can never be enough, and at least five are required.

Five only works if the seven gaps can actually be cut from five rails without any piece spanning two rails. The two 210 cm gaps each leave only 30 cm spare on a 240 cm rail – not enough for any other gap – so each needs a rail to itself; the 180 cm gap is the same story, with only 60 cm spare. That is already three rails used up. The remaining two rails carry the last four gaps: 150 + 90 = 240 cm exactly on one, and 120 + 115 = 235 cm on the other (5 cm left over). All seven gaps are accounted for using exactly five rails, matching the minimum of five found above.

So the smallest number of rails the farmer could use is 5.

Summary to learn

“Minimum number of pieces” cutting problems (fence rails, pipe sections, wallpaper strips) are solved in two separate steps: first find a hard lower bound by comparing the total length needed against the maximum length available from fewer pieces, and then confirm that bound is actually achievable by constructing one real cutting plan that uses exactly that many pieces without any single gap needing material from two different pieces.

Undercover police investigators sometimes commit ‘crimes’ in order to convince the ‘real criminals’ that they are on the same side as them. Some of these activities have victims, although in the main these are other criminals — rival gang members for example. In committing what are technically offences the officers are preventing many more serious crimes by helping to convict and imprison dangerous criminals who might otherwise remain at liberty. But that is not really the point. A breach of the law is a breach of the law, whoever commits it and for whatever reason. Preventing a crime does not make it right to commit another crime.

Which one of the following is the general principle underlying the above argument?

  • AAn act is criminal only if it is committed for criminal reasons.
  • BSerious crime must be prevented by any reasonable means.
  • CThe police have a duty to protect law abiding citizens from violence.
  • DThere is no such thing as a victimless crime.
  • EThe end does not justify the means.
Correct answer: E The end does not justify the means.

Full explanation

The principle comes from the statement that says breach of the law is a breach of the law, whoever commits it and for whatever reason. So, doing something wrong (breaking the law) is not justified by the good results it might produce (catching criminals).

Analysis of the given options

Option A : Incorrect. The passage says any breach of the law is wrong, regardless of intention.

Option B : Incorrect. This supports committing minor crimes to stop bigger ones — opposite to the argument!

Option C : Incorrect. This is a true statement but not the principle discussed in this passage.

Option D : Incorrect. Mentioned briefly (victims being other criminals), but not the main focus.

Option E : Matches exactly — committing a crime is still wrong, even if it prevents worse outcomes.

Summary to learn

A general principle behind an argument is the abstract rule it is applying, stripped of its specific subject matter — here, “a rule someone is bound by does not become acceptable to break just because breaking it produces a good outcome.” Identifying the correct underlying principle means finding the option that states this same general trade-off, not an option that only shares surface-level themes like crime, danger, or law enforcement.

Deanna keeps a record of the petrol she puts into her car and the current distance it has covered so she can estimate her fuel consumption. When she puts petrol in, sometimes the tank is filled completely and she marks ‘FULL’ beside the entry if this is so, otherwise the tank is only partly filled.

Her data for the last month is as follows:

IMAT 2015 question 19 figure
Which one of the following is the best estimate of her fuel consumption?

  • A9.9 litres / 100 km
  • B7.7 litres / 100 km
  • C1.7 litres / 100 km
  • D6.8 litres / 100 km
  • E8.0 litres / 100 km
Correct answer: D 6.8 litres / 100 km

Full explanation

To calculate the fuel consumption, we will use the data starting from the day with the full tank of fuel till another date with the full fuel tank.

From 6th to 23rd June, total distance covered = 24,989 − 23,805=1,184 km Total liters of fuel added = 25 + 21 + 34 = 80 L Fuel consumption = (80L)/(1,184 km ) For 1,184 km — 80 L of fuel consumed For 100 km — 80 × (100)/(1,184) = (8000)/(1,184) =nearly 7 So, the best estimate of her fuel consumption is 6.8 litres / 100 km

Summary to learn

Estimating a rate (like fuel consumption per 100 km) from a log of partial refills requires measuring only between two points where the tank was known to be in the same state — typically two “FULL” entries — since only then does the total fuel added over that stretch equal the total fuel actually consumed; refills made between two full-ups, plus the fill-up that tops the tank back up at the end of the stretch, are what get summed, while measuring from an arbitrary partial fill would introduce an unknown starting amount into the calculation.

A local museum wishes to exhibit a collection of butterflies which is mounted in nine narrow (only 0.2 m wide) display cases, each 1.5 m long. The museum wants to arrange four tables, each 2 m long and 1 m wide, in such a way that all the display cases can be placed around the edges. The room for the exhibition is 6 m by 6 m and there must be at least 1 m of clear floor space around the outside of the tables.

Which one of the five arrangements shown would be satisfactory?

  • A
    IMAT 2015 question 20 answer option A
  • B
    IMAT 2015 question 20 answer option B
  • C
    IMAT 2015 question 20 answer option C
  • D
    IMAT 2015 question 20 answer option D
  • E
    IMAT 2015 question 20 answer option E
Correct answer: C

Full explanation

Each of the four 2 m × 1 m tables can have display cases placed only around its outer edges (not where tables touch each other or the wall), and the room’s 6 m × 6 m floor must keep at least 1 m of clear space around the whole table arrangement.

Option A (an L-shaped block of tables) and option C’s alternative single-block layouts each only expose enough edge length for 4 display cases, not all 9. Option B’s layout (four tables end-to-end, 8 m long) and the bottom U-shaped layout (6 m across) are both too large to fit in the room with the required 1 m clearance on every side.

Only the U-shaped arrangement shown in option C (two tables forming the base, one table forming each side) exposes enough outer edge to fit all nine 1.5 m display cases around it, while still fitting inside the 6 m × 6 m room with 1 m of clear space on every side.

Therefore, option C is the satisfactory arrangement.

Summary to learn

Fitting objects into a bounded space under several simultaneous requirements — a maximum footprint, a minimum clearance margin around everything, and a minimum total length of usable edge or perimeter — means every one of those requirements has to hold for the SAME layout at once. A candidate arrangement that comfortably satisfies one requirement (say, overall size) can still fail a completely different one (like not exposing enough edge length for the number of items that need to sit along it) — geometric packing problems like this are conjunctions of constraints, not a single measurement to optimise.

Which one of the following pairs of scholar/field of study is NOT correct?

  • AAmartya Sen Economics
  • BKonrad Lorenz Ethology
  • CDoris Lessing Literature
  • DMax Weber Pedagogy
  • ELudwig Wittgenstein Philosophy
Correct answer: D Max Weber Pedagogy

Full explanation

Max Weber was mainly known for Sociology and Economics, not education (pedagogy).

Summary to learn

Well-known scholars are strongly associated with the field that made them famous: Amartya Sen with economics, Konrad Lorenz with ethology (the study of animal behaviour), Doris Lessing with literature, and Ludwig Wittgenstein with philosophy. Max Weber, despite writing on many social topics, is principally known as a founding figure of sociology (and economics), not pedagogy (education theory).

Which one of the following public figures was NOT awarded the Nobel Peace Prize?

  • AAung San Suu Kyi
  • BNelson Mandela
  • CWilly Brandt
  • DMahatma Gandhi
  • EMartin Luther King
Correct answer: D Mahatma Gandhi

Full explanation

Mahatma Gandhi is nominated several times but never awarded.

Summary to learn

The Nobel Peace Prize has been awarded to figures such as Aung San Suu Kyi, Nelson Mandela, Willy Brandt, and Martin Luther King for their work advancing peace and human rights. Mahatma Gandhi, despite being closely associated with nonviolent activism and nominated for the prize multiple times, was never actually awarded it.

Biology

Cell biology, genetics, molecular biology & human physiology · 18 questions
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The changes in concentration of hormones in a healthy woman’s blood were monitored during several menstrual cycles.

During which stage of the menstrual cycle was the concentration of oestrogen falling, the concentration of luteinising hormone (LH) and follicle stimulating hormone (FSH) maximal and the progesterone concentration rising?

  • Aat the start of menstruation
  • Bat the end of menstruation
  • Cfour days before ovulation and the time of ovulation
  • Dafter ovulation but before the start of menstruation
  • Ebetween the end of menstruation and four days before ovulation
Correct answer: C four days before ovulation and the time of ovulation

Full explanation

IMAT 2015 question 23 figure

Image from KAPLAN MCAT Biology review

The stage when the concentration of oestrogen falling, the concentration of luteinising hormone (LH) and follicle stimulating hormone (FSH) maximal and the progesterone concentration rising is around the time of ovulation.

Therefore, appropriate answer is C. four days before ovulation and the time of ovulation

Summary to learn

The menstrual cycle is coordinated by a sequence of hormone changes. In the days leading up to ovulation, oestrogen from the developing follicle rises and then triggers a sharp surge in luteinising hormone (LH) and follicle stimulating hormone (FSH); ovulation itself is triggered by this LH surge. Immediately afterward, oestrogen briefly falls while LH and FSH are still near their peak, and the ruptured follicle (now the corpus luteum) begins secreting progesterone, which then rises through the post-ovulation phase to help maintain the uterine lining.

The following events occur during a reflex response to a person placing a hand on a hot object.

1. Myosin binding sites on actin filaments uncovered.

2. ADP and phosphate ion released from myosin head.

3. Sodium voltage gated channels open.

4. Myosin head detaches from binding site on actin.

5. Calcium ions released by sarcoplasmic reticulum.

Which of the following options places four of these events in the correct order (from left to right)?

  • A3, 5, 4, 2
  • B5, 2, 1, 4
  • C1, 2, 4, 3
  • D5, 1, 2, 4
  • E3, 1, 4, 2
Correct answer: D 5, 1, 2, 4

Full explanation

5 events are given and we have to order 4 for a reflex response.

When a person touches a hot object, he withdraws his hand immediately. So, a muscle contraction occurs in his hand. Steps of muscle contraction are

– Calcium ions are released by sarcoplasmic reticulum

– As a result, myosin binding sites on actin filaments uncovered.

– Myosin binds to actin

– Powerstroke occurs when ADP and phosphate ion dissociate from myosin.

– Then, new ATP binds to myosin, causing detachment of myosin from actin.

Sodium voltage gated channel opening occurs during the action potential so it is an unrelated event to the muscle contraction phase.

So, the correct order of events would be D. 5, 1, 2, 4

IMAT 2015 question 24 figure
Image from KAPLAN MCAT Biology review book

Summary to learn

Muscle contraction (excitation-contraction coupling) follows a fixed sequence: an action potential (via voltage-gated sodium channels) travels down the neuron and triggers calcium release from the sarcoplasmic reticulum; this calcium exposes the myosin-binding sites on actin (previously blocked by tropomyosin); myosin heads then bind actin and, using energy from ATP hydrolysis, release their bound ADP and phosphate during the power stroke that pulls the actin filament inward; finally, a fresh ATP molecule binds the myosin head, causing it to detach from actin so the cycle can repeat.

The genotype QqRr produces a certain phenotype. If two individuals with a genotype of QqRr reproduce, how many different possible phenotypes could be created, assuming all allele combinations are equally viable and the phenotypes are the result of complete dominance?

  • A16
  • B4
  • C5
  • D8
  • E9
Correct answer: B 4

Full explanation

If two individuals with a genotype of QqRr reproduce — meaning when 2 heterozygous dihybrids (QqRr x QqRr) are crossed, the phenotypic ratio is 9:3:3:1. (You can always write a punnett square for each cross but it is recommended to memorize the typical phenotypic ratios of a dihybrid cross. )

The 9:3:3:1 ratio indicates the presence of four distinct phenotypes, each occurring in different proportions. So, 4 different possible phenotypes could be created from this cross.

Summary to learn

In a dihybrid cross between two individuals heterozygous for two independently assorting genes (Aa Bb × Aa Bb), complete dominance at both loci produces the classic 9:3:3:1 phenotypic ratio: four distinct phenotype classes (dominant-dominant, dominant-recessive, recessive-dominant, recessive-recessive) in that proportion, regardless of what the underlying alleles specifically control.

A double stranded DNA molecule is shown below:

IMAT 2015 question 26 figure
This DNA molecule is allowed to replicate three times in a medium containing nonradioactive nucleotides .

Which answer shows the correct percentages of original DNA and completely non radioactive DNA?

IMAT 2015 question 26 figure
[Assume all radioactive nucleotides remain radioactive throughout, and all non radioactive nucleotides remain nonradioactive throughout].

  • Arow 4
  • Brow 1
  • Crow 5
  • Drow 3
  • Erow 2
Correct answer: B row 1

Full explanation

Look closely at the starting molecule in the diagram before doing any arithmetic: it is not fully radioactive to begin with. One strand is already made of radioactive nucleotides and the other of ordinary, non-radioactive ones. That detail matters a lot, because from this point onward the only thing you can actually detect is radioactivity – the original non-radioactive strand looks exactly like every brand-new strand made later in the non-radioactive medium. So “percentage of original DNA” in the answer table really means “percentage of molecules that still carry the one traceable radioactive strand”, not “percentage of molecules containing either original strand”.

DNA replication is semi-conservative: whenever a duplex separates, each of its two strands keeps its own partner intact and gets a brand new complementary strand built alongside it from whatever nucleotides are floating in the medium – all non-radioactive here. Crucially, the radioactive strand itself is never duplicated into a second radioactive strand; it is one single, unbroken piece of DNA that just keeps getting handed down, generation after generation, always paired with a fresh non-radioactive partner.

Trace it round by round. Start: 1 molecule = 1 radioactive strand + 1 non-radioactive strand.

Round 1: the two strands separate and each builds a new non-radioactive partner. Result: 2 molecules total, and the one radioactive strand is now sitting in just one of them – the other molecule is entirely non-radioactive.

Round 2: all molecules from round 1 separate and rebuild the same way. Of the 4 molecules that result, only the single one that inherited the radioactive strand can produce another molecule still carrying it; every other new molecule is built from strands that were already non-radioactive, so it stays completely non-radioactive. Result: 4 molecules, and still only 1 of them carries the radioactive strand.

Round 3: the same logic repeats once more, because the radioactive strand can only ever be handed down into one daughter molecule per round, no matter how many rounds pass. Result: 8 molecules total, and still only 1 of them carries the radioactive strand.

So after three rounds of replication: 1 out of 8 molecules is still traceably “original” (1/8 × 100% = 12.5%), and the remaining 7 out of 8 are completely non-radioactive (7/8 × 100% = 87.5%).

12.5% original and 87.5% completely non-radioactive is exactly row 1, so the answer is (B).

Summary to learn

DNA replication is semi-conservative: each parent strand of a duplex stays intact and pairs with a newly synthesised complementary strand. If only one of the two original strands is radioactively labelled (not both), that single traceable strand is never duplicated into a second radioactive strand — it is simply handed down to exactly one daughter molecule every round of replication. So after n rounds there are 2ⁿ molecules total, but still only ever 1 of them contains the original radioactive strand: after 3 rounds, that is 1 of 8 molecules (12.5%) still “original,” and 7 of 8 (87.5%) completely non-radioactive.

Which of the following are directly produced during photolysis of water?

1. Oxygen 2. carbon dioxide 3. Protons

  • A1 only
  • B2 and 3 only
  • C1 and 3 only
  • D1 and 2 only
  • E2 only
Correct answer: C 1 and 3 only

Full explanation

Photolysis of water is a process that occurs in the thylakoid lumen during the light-dependent reactions of photosynthesis.

Direct products

– Oxygen : yes, released as a byproduct into the atmosphere.

– Carbon dioxide : no, CO₂ is used in the Calvin cycle (light-independent reactions), not produced during photolysis.

– Protons (H⁺) : yes, Released into the thylakoid lumen, contributing to the proton gradient for ATP synthesis.

Therefore, the correct option is C. 1 and 3 only

Summary to learn

Photolysis is the light-driven splitting of water during the light-dependent reactions of photosynthesis, occurring in the thylakoid membrane. It directly yields oxygen gas (released as a byproduct), protons/H⁺ (which build up in the thylakoid lumen to drive ATP synthase), and electrons (which replace those lost by chlorophyll). Carbon dioxide plays no part in photolysis; it is instead used later, in the light-independent reactions (Calvin cycle) taking place in the stroma.

In the nerve cells of a person, one gene has two alleles, ‘A’ and ‘a’, present. For this person, which row correctly shows the alleles present in all three different situations given in the table?

IMAT 2015 question 28 figure
  • Arow 1
  • Brow 2
  • Crow 5
  • Drow 4
  • Erow 3
Correct answer: A row 1

Full explanation

In this individual, the gene is heterozygous with the alleles Aa (one ‘A’ on one homologous chromosome and one ‘a’ on the other).

In stem cells beginning to specialise into a liver cell, the cell is in a non-replicating state, so it will have one ‘A’ and one ‘a’ — represented as Aa.

In a cell at the start of mitosis, DNA replication has already occurred during the S phase of interphase. As a result, each chromosome has been duplicated, so the cell now contains AAaa (two identical sister chromatids for each homologous chromosome).

In a cell at the start of meiosis I, DNA replication has also occurred during the S phase, so the genetic content is likewise AAaa.

Thus, the correct row is row 1 (option A)

Summary to learn

Whether a diploid cell’s allele content is written as “Aa” or “AAaa” depends only on whether DNA replication (S-phase) has already occurred, not on which stage of division the cell is heading toward. An unreplicated diploid cell (such as a resting stem cell before its own S-phase) has one copy of each homologous chromosome and so is simply Aa. Once S-phase duplicates every chromosome into two sister chromatids, the same genetic content becomes AAaa — and a cell freshly entering either mitosis or meiosis I has, by definition, already passed through S-phase, so both are AAaa.

The diagram shows a single sarcomere in a relaxed state.

IMAT 2015 question 29 figure
Which answer describes the changes when the sarcomere contracts?

  • A1 gets smaller and 2 gets smaller.
  • B1 gets smaller and 2 does not change.
  • C1 gets longer and 2 gets smaller.
  • D1 does not change and 2 gets wider.
  • E1 gets longer and 2 gets wider.
Correct answer: B 1 gets smaller and 2 does not change.

Full explanation

Muscle contraction works by the sliding filament model: thin (actin) filaments slide past thick (myosin) filaments, pulled inward by repeated myosin cross-bridge cycling, without either type of filament itself changing length.

Label 1 spans the whole sarcomere, from one Z-line to the other – this is the unit that physically shortens during contraction, since pulling the Z-lines closer together is exactly what “the muscle contracting” means at this scale.

Label 2 spans the myosin (thick filament) zone. Myosin filaments are rigid structural proteins that do not stretch or shrink during contraction – only their degree of overlap with the sliding actin filaments changes – so the length of this zone stays the same before and after contraction.

So during contraction: label 1 (the whole sarcomere) gets smaller, while label 2 (the myosin/thick-filament zone) does not change. That is option B.

Summary to learn

A sarcomere — the basic contractile unit of a muscle fibre, bounded by two Z-lines — shortens during contraction as the actin (thin) and myosin (thick) filaments slide past one another (the sliding filament model), pulling the Z-lines closer together. The individual filaments themselves do not change length during this process; only the amount of overlap between them, and hence the overall sarcomere length, changes.

The diagram below shows an amino acid.

IMAT 2015 question 30 figure
Which option correctly identifies both the variable group (R group) and the acidic group?

  • Avariable group = 4; acidic group = 3
  • Bvariable group = 3; acidic group = 1
  • Cvariable group = 2; acidic group = 3
  • Dvariable group = 1; acidic group = 2
  • Evariable group = 2; acidic group = 4
Correct answer: C variable group = 2; acidic group = 3

Full explanation

In an amino acid, there is the carboxyl group (-COOH) which is the acidic group, the amino group, hydrogen atom and a variable group.

In the given image, the variable group is indicated by label number 2 and the acidic group is indicated by label number 3.

The given amino acid is Alanine.

Summary to learn

Every standard amino acid shares the same core structure: a central (alpha) carbon bonded to an amino group (−NH₂), a carboxyl group (−COOH, the molecule’s acidic group, since it can donate a proton), a hydrogen atom, and a variable R group that differs between amino acids and gives each one its distinct chemical properties. The carboxyl group is always the acidic group; the R group is always the variable one, regardless of which specific amino acid is shown.

Where in a shoulder joint are osteocytes found?

  • Amuscle tissue
  • BLigament
  • CCartilage
  • Dbone tissue
  • Eskin
Correct answer: D bone tissue

Full explanation

Osteocytes are mature bone cells found within bone tissue, where they maintain the bone matrix. They live in small spaces called lacunae within the hard, mineralized matrix of bone.

– Muscle tissue — contains muscle fibers, no osteocytes.

– Ligament — made of dense regular connective tissue, no osteocytes.

– Cartilage — contains chondrocytes, not osteocytes.

– Skin — made of epithelial and connective tissue layers, no osteocytes.

Summary to learn

Osteocytes are mature bone cells embedded within the mineralized bone matrix, housed in small spaces called lacunae, where they help maintain that matrix. They are specific to bone tissue and are not found in the other connective and soft tissues of a joint: cartilage contains chondrocytes instead, ligaments are made of dense connective tissue with fibroblasts, muscle contains muscle fibres, and skin is epithelial and connective tissue — none of these tissue types contain osteocytes.

The picture below shows a DNA microarray. Each spot (labelled 1–4) contains a different DNA probe. A sample of fluorescently labelled human DNA, with the sequence TGGTCAAGATTAT, is washed over the array.

IMAT 2015 question 32 figure
IMAT 2015 question 32 figure
Which of the spots would show a positive signal because it fluoresces?

  • A1, 2, 3 and 4
  • B2 and 3 only
  • C1 and 3 only
  • D1 and 4 only
  • E2 and 4 only
Correct answer: B 2 and 3 only

Full explanation

A sample of fluorescently labelled human DNA, with the sequence TGGTCAAGATTAT, is washed over the array that contains 4 spots with different DNA probes. So, hydrogen bonding will occur if the DNA found a complementary sequence in each probe.

The probes are GATTAT, CTAATA, ACCAGT, and TGGTCA Complementary strand of given DNA would be ACCAGTTCTAATA So, it can be seen that a segment of it has a similar sequence with probe in spot 2 and a segment similar to probe in spot 3.

Therefore, these 2 spots (2 and 3) would show a positive signal.

Summary to learn

A DNA probe on a microarray only fluoresces (gives a positive signal) if a complementary strand of the labelled sample DNA can base-pair with it via ordinary Watson-Crick pairing (A with T, G with C). Working out which probes will light up means writing out the complementary sequence of the sample DNA in full and then checking, spot by spot, whether that complementary sequence contains a run matching that spot’s specific probe sequence — only the spots with a genuine complementary match fluoresce; the rest do not.

The diagram shows how the pressure changes in the left atrium, left ventricle and the aorta during one heartbeat in a healthy human.

IMAT 2015 question 33 figure
Which row shows the correct events during time period X?

IMAT 2015 question 33 figure
  • Arow 2
  • Brow 3
  • Crow 5
  • Drow 4
  • Erow 1
Correct answer: E row 1

Full explanation

During period X, which represents atrial contraction, the volume of blood in the left atrium decreases as it is pushed into the left ventricle. During this time, the semilunar valves remain closed and the ventricles are relaxed.

Therefore, the correct row is row 1.

Summary to learn

During a single heartbeat, atrial pressure, ventricular pressure and aortic pressure rise and fall in a fixed sequence tied to valve movement. During atrial contraction (late diastole), the atrium pushes its remaining blood into the relaxed ventricle, so atrial blood volume falls; the ventricles are still relaxed and not yet generating enough pressure to open the semi-lunar (aortic) valve, so it stays closed throughout this phase. Once ventricular contraction begins afterward, pressure inside the ventricle rises sharply, eventually forcing the semi-lunar valve open once it exceeds aortic pressure.

The table shows some events of the normal eukaryotic cell cycle.

IMAT 2015 question 34 figure
Which row shows the correct sequence of events (left to right) as they occur during part of this cell cycle?

  • Arow 5
  • Brow 2
  • Crow 1
  • Drow 4
  • Erow 3
Correct answer: E row 3

Full explanation

During the cell cycle, especially in the mitosis phase, 5 processes can be seen in order.

– Prophase : Nuclear envelope disappears and DNA starts to condense.

– Metaphase : Chromosomes align at the equator

– Anaphase : Chromosomes separate and spindle fibers shorten.

– Telophase : nuclear membrane reforms

– Cytokinesis : division of cytoplasm

So, according to this order, the correct sequence of events is shown in row 3.

Summary to learn

Mitosis proceeds through a fixed order of visible events. In prophase, the nuclear envelope breaks down and DNA condenses into visible chromosomes. In metaphase, those chromosomes line up at the cell’s equator. In anaphase, spindle fibres shorten, pulling the sister chromatids to opposite poles. In telophase, the nuclear envelope reforms around each new set of chromosomes. Finally, in cytokinesis, the cytoplasm itself divides, completing the formation of two separate daughter cells.

Which one of the following is NOT a carbohydrate?

  • AGlucagon
  • BAmylose
  • CRibose
  • DAmylopectin
  • EMaltose
Correct answer: A Glucagon

Full explanation

Glucagon — Not a carbohydrate. It’s a peptide hormone made of amino acids, produced by the pancreas to raise blood glucose levels.

Amylose — A polysaccharide (a type of starch made of glucose units).

Ribose — A pentose monosaccharide (5-carbon sugar), part of RNA.

Amylopectin — A highly branched polysaccharide (another component of starch).

Maltose — A disaccharide made of two glucose molecules.

Summary to learn

Carbohydrates in biology span single sugars (monosaccharides, like the 5-carbon sugar ribose), pairs of linked sugars (disaccharides, like maltose, two glucose units joined together), and long branched or unbranched chains of sugar units (polysaccharides, like amylose and the more highly branched amylopectin, both components of starch). Glucagon, despite its glucose-related name, is not a carbohydrate at all — it is a peptide hormone made of amino acids, secreted by the pancreas to raise blood glucose levels.

Some local anaesthetics affect nervous impulse transmission by making it more difficult for voltage gated sodium channels to open. In a human patient treated with these anaesthetics, which of the following statements would be true?

  • AThe threshold potential required to generate an action potential would be lowered.
  • BThe axon membrane would become more difficult to repolarise.
  • CIt would become harder to depolarise the neuron.
  • DThe membrane potential of the neuron at rest would decrease below -90 mV.
  • EThe sodium/potassium pump may need to work faster to maintain the resting potential.
Correct answer: C It would become harder to depolarise the neuron.

Full explanation

Voltage-gated Na⁺ channels = Open during depolarization → Na⁺ rushes in → action potential is triggered.

Local anaesthetics = Make it harder for these Na⁺ channels to open → harder for neuron to fire.

Analysis of the given options Option A : False. Lowering the threshold means neurons fire more easily. But anaesthetics make firing harder.

Option B : False. Repolarisation mainly involves K⁺ channels opening. Anaesthetics are affecting Na⁺ channels, not K⁺ ones.

Option C : True. Since Na⁺ entry (needed for depolarization) is blocked, depolarization is harder.

Option D : Resting potential (\~-70 mV) is mainly set by K⁺ leak channels and Na⁺/K⁺ pumps, not voltage-gated Na⁺ channels. Anaesthetics don’t affect this significantly.

Option E : There’s less Na⁺ movement into the cell with anaesthetic use → less work for the Na⁺/K⁺ pump, not more.

Summary to learn

An action potential’s rising phase (depolarisation) depends entirely on voltage-gated sodium channels opening so Na⁺ can rush into the neuron. A drug that makes it harder for those channels to open directly makes it harder to depolarise the neuron and trigger a signal, without necessarily changing the resting membrane potential (set mainly by K⁺ leak channels and the Na⁺/K⁺ pump) or repolarisation (which depends on separate voltage-gated potassium channels, not sodium channels).

Place the following structures in a human sperm cell in descending order of size (left to right):

1. Mitochondria 2. Nucleus 3. Ribosome

  • A1, 2, 3
  • B1, 3, 2
  • C3, 1, 2
  • D2, 3, 1
  • E2, 1, 3
Correct answer: E 2,1,3

Full explanation

In the cell, the largest organelle is typically the nucleus. So, even if you don’t remember the actual size of the nucleus which is around 5μm, you can guess.

Ribosomes should be considerably smaller than mitochondria because they solely synthesize proteins one by one while mitochondria involve a large number of enzyme complexes that operate the energy producing mechanism.

So, the order in descending size is 2,1,3

Summary to learn

Cell structures span an enormous range of sizes: the nucleus (holding the full genome) is typically the largest organelle in a cell, at several micrometres across; mitochondria are smaller, mid-sized organelles built around a comparatively large set of enzyme complexes for producing ATP; and ribosomes, tiny complexes of rRNA and protein that assemble proteins one amino acid at a time, are smaller still.

In a prokaryote, transcription can occur in which of the following?

1. Cytoplasm 2. Mitochondria 3. Ribosomes

  • A3 only
  • B1 and 3 only
  • C1 only
  • D1 and 2 only
  • E2 only
Correct answer: C 1 only

Full explanation

In a prokaryote, there are no membrane bound organelles, so, we can exclude mitochondria which is a double membrane bounded organelle.

Ribosomes are sites of protein synthesis or translation, not transcription.

So, transcription only occurs in the cytoplasm in prokaryotes.

Summary to learn

Transcription requires access to the cell’s genetic material (DNA) together with the enzymes and building blocks that synthesise RNA from it. In a prokaryote, which has no membrane-bound organelles at all, this can only happen in the cytoplasm, where the DNA is located; mitochondria (a eukaryote-only, membrane-bound organelle) don’t exist in prokaryotes, and ribosomes are the site of translation (protein synthesis from mRNA), not transcription, in any cell type.

A normal sequence of triplets in a section of DNA is given by: ATCGAACGG

The same section of DNA has been changed by mutation, and is given by: ATCTTGCGG Some of the triplets below represent the tRNA triplets which code for amino acids.

Key:

IMAT 2015 question 39 figure
Using the tRNA triplets, which amino acid sequence given below could be formed from the mutated DNA sequence?

  • A
    IMAT 2015 question 39 answer option A
  • B
    IMAT 2015 question 39 answer option B
  • C
    IMAT 2015 question 39 answer option C
  • D
    IMAT 2015 question 39 answer option D
  • E
    IMAT 2015 question 39 answer option E
Correct answer: C Open square – open circle – open diamond

Full explanation

Mutated DNA sequence — ATCTTGCGG

Transcripted mRNA — UAGAACGCC

tRNA triplets — AUC UUG CGG

Therefore, the correct amino acid sequence is

IMAT 2015 question 39 figure

Summary to learn

Working from a DNA sequence to a final amino acid (or symbol) sequence is a multi-step translation chain: transcribe the DNA template into a complementary mRNA sequence, group that mRNA into triplets (codons), find the complementary tRNA anticodon triplet for each codon, and finally look up what each tRNA triplet specifies using the given key. Each step must use correct complementary base pairing (A↔T in DNA, A↔U and T↔A between DNA and RNA, C↔G throughout) or the final answer will be wrong even if every other step is done correctly.

Which of the following could be the outcome of evolution?

1. Speciation 2. a change in allele frequency 3. increased biodiversity

  • A2 and 3 only
  • B1 only
  • C1 and 3 only
  • D1, 2 and 3
  • E1 and 2 only
Correct answer: D 1, 2 and 3

Full explanation

Outcome of evolution

1. Speciation : Yes — Evolution over time can lead to the formation of new species (speciation).

2. a change in allele frequency : Yes — Evolution is a change in allele frequencies in a population over time.

3. increased biodiversity : Yes — Speciation and adaptation to different niches can increase the variety of life forms (biodiversity).

Summary to learn

Evolution is fundamentally a change in a population’s allele frequencies over time, and several related phenomena can all be understood as outcomes flowing from that same underlying process: sustained divergence can eventually produce new species (speciation), and as populations diverge and adapt to different niches, the overall variety of life forms present (biodiversity) tends to increase as well.

Chemistry

General, inorganic, organic & biochemistry · 12 questions
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0.75 g of a hydrocarbon compound contains 0.60 g of carbon.

(Ar : C = 12.0; H = 1.0)

Which one of the following could be the molecular formula of the hydrocarbon compound?

  • AC₃H₈
  • BC₂H₄
  • CC₂H₆
  • DCH₄
  • EC₂H₃
Correct answer: C C₂H₆

Full explanation

Total mass of compound = 0.75 g

Mass of carbon = 0.60 g

Mass of hydrogen = 0.75 g — 0.60 g = 0.15 g

– Convert mass to moles

Moles of carbon = (0.60 g)/(12 g/mol ) = 0.050 mol

Moles of hydrogen = (0.15g)/(1.0g/mol) = 0.15 mol

– Find simplest whole number ratio of the moles

Carbon : Hydrogen

0.050 mol : 0.15 mol

1 : 3

So, the empirical formula is CH₃.

From the given options, possible molecular formula is (CH₃​)2 ​= C₂H₆

Summary to learn

Finding a compound’s molecular formula from mass data starts by finding the empirical formula: convert each element’s mass to moles using its molar (atomic) mass, then divide every mole value by the smallest one to get the simplest whole-number ratio of atoms. Since the true molecular formula must be some whole-number multiple of that empirical formula, the final step is checking which multiple, if any, actually appears among the given answer options.

In the reaction

C₃H₇Br + KOH → C₃H₇OH + KBr 24.6 g of 1- bromopropane reacts with excess potassium hydroxide to produce 8.00 g of propan-1-ol.

Mr : C₃H₇Br = 123 Ar : H = 1.0 ; C = 12.0 ; O = 16.0 What is the percentage yield of this reaction?

  • A57.1%
  • B93.0%
  • C32.5%
  • D33.3%
  • E66.7%
Correct answer: E 66.7%

Full explanation

C₃H₇Br + KOH → C₃H₇OH + KBr

Given mass of C₃H₇Br = 24.6g

Molar mass (Mr) = 123

Moles of C₃H₇Br = (24.5)/(123) = 0.200 mol

From the balanced equation: 1 mol of C₃H₇Br produces 1 mol of C₃H₇OH So, 0.200 mol of C₃H₇Br should produce 0.200 mol of C₃H₇OH.

Molar mass of C₃H₇OH = 3×12+8×1+16 = 60 g/mol

Theoretical yield of Propan-1-ol (C₃H₇OH) = 0.200 x 60 = 12.0 g

Actual yield given = 8.00 g

Percentage yield = (Actual yield )/(Theoretical yield ) × 100 = (8)/(12) × 100 = 66.7%

Summary to learn

Percentage yield compares how much product a reaction actually produced (the actual yield, as measured) against the maximum amount predicted by stoichiometry from the limiting reagent (the theoretical yield): the calculation is (actual yield ÷ theoretical yield) × 100%. Finding the theoretical yield itself requires converting the starting reagent’s mass into moles, applying the balanced equation’s mole ratio to find moles of product, and converting that back into a mass using the product’s own molar mass.

Pure water self ionizes. This endothermic reaction is represented by the equation:

H₂O(l) ⇌ H⁺(aq) + OH⁻(aq)

Which of the following statements is true for pure water between the temperatures of 0 °C and 100 °C?

1. The concentrations of H+(aq) and OH–(aq) are equal between 0 °C and 100 °C.

2. An increase in temperature causes the pH to fall.

3. An increase in temperature causes the electrical conductivity to decrease.

  • A1 and 3 only
  • B3 only
  • C1 only
  • D1 and 2 only
  • E2 only
Correct answer: D 1 and 2 only

Full explanation

Given reaction : H₂O(l) ⇌ H⁺(aq) + OH⁻(aq)

It is an endothermic reaction.

According to Le Chatelier’s Principle, adding heat (increasing temperature) will shift equilibrium to the right, producing more H⁺ and OH⁻ ions.

Analysis of the given options

1. The concentrations of H+(aq) and OH–(aq) are equal between 0 °C and 100 °C. True. Pure water is always neutral by definition, meaning: [H⁺] = [OH⁻], even if their individual concentrations increase with temperature, they stay equal.

2. An increase in temperature causes the pH to fall. True. More H⁺ ions are produced when temperature increases.

Higher [H⁺] → lower pH (because pH=−log⁡[H⁺]).

Thus, pH falls as temperature increases, even though the solution remains neutral.

3. An increase in temperature causes the electrical conductivity to decrease.

False. As temperature increases ➔ more ionization ➔ higher conductivity.

Summary to learn

Le Chatelier’s principle predicts how an equilibrium reacts to a temperature change: raising the temperature always shifts the equilibrium position toward whichever direction absorbs heat (the endothermic direction). Since water’s self-ionisation is endothermic in the forward direction, warming water drives more H⁺ and OH⁻ ions into solution — but because they are always produced in a strict 1:1 ratio from water itself, the solution stays perfectly neutral ([H⁺] = [OH⁻]) at every temperature, even though a higher [H⁺] means a numerically lower pH and greater ionic concentration means higher electrical conductivity.

The atomic number of aluminium is 13.

Which electron configuration given below corresponds to the Al²⁺ ion in its ground state?

  • A1s² 2s² 2p⁶ 3s² 3p¹
  • B1s² 2s² 2p⁶ 3s² 3p³
  • C1s² 2s² 2p⁶
  • D1s² 2s² 2p⁶ 3s¹
  • E1s² 2s² 2p⁵ 3s²
Correct answer: D 1s² 2s² 2p⁶ 3s¹

Full explanation

For aluminium, atomic number is 13, so:

Al : 1s² 2s² 2p⁶ 3s² 3p¹

An Al²⁺ ion means 2 electrons are removed from neutral aluminium.

After removing 2 electrons:

Al²⁺ : 1s² 2s² 2p⁶ 3s¹

Summary to learn

An atom’s ground-state electron configuration is built by filling orbitals in order of increasing energy (1s, 2s, 2p, 3s, 3p, …), with the total electron count matching the atomic number for a neutral atom. Forming a positive ion of charge n+ means removing exactly n electrons from that neutral configuration, always taken from the highest-energy (outermost) occupied subshell first, which is exactly what distinguishes a cation’s configuration from its parent neutral atom’s.

Atoms X and Y form an ionic compound with formula XY₂.

Which option below could give the correct atomic numbers for X and Y?

  • AX = 11; Y = 16
  • BX = 3; Y = 17
  • CX = 12; Y = 9
  • DX = 6; Y = 16
  • EX = 14; Y = 8
Correct answer: C X = 12; Y = 9

Full explanation

The formula XY₂ tells us:

1 atom of X combines with 2 atoms of Y

This means :

Charge on X = +2 and each Y = -1

Alkaline earth metals usually have +2 oxidation number and halogens usually have -1 oxidation numbers.

Alkaline earth metals have atomic numbers — 4,12,20, …

Halogens have atomic numbers — 9,17, …

Among the given options, the one whose atomic numbers match an alkaline earth metal and a halogen is option C: X = 12 (magnesium) and Y = 9 (fluorine)

Summary to learn

An ionic compound’s formula reflects how many ions of each charge are needed to balance out to a neutral overall compound: in a compound XY₂, X must carry a +2 charge and each Y must carry a −1 charge for the charges to cancel. Group 2 elements (alkaline earth metals, such as those with atomic numbers 4, 12, 20) reliably form +2 ions, and group 17 elements (halogens, such as those with atomic numbers 9, 17) reliably form −1 ions, which is why identifying an element’s group from its atomic number is the key step in this kind of problem.

2,2 — dimethylpropane, C(CH₃)₄, is an isomer of pentane, CH₃(CH₂)₃CH₃.

Pentane has a boiling point of 36 °C whilst the boiling point of 2,2 — dimethylpropane is 10 °C.

Which statement below explains the difference in the boiling points for these two substances?

  • A2,2 — dimethylpropane has stronger intermolecular forces.
  • BThe molecules have different relative molecular masses.
  • CIsomers have different chemical properties.
  • DPentane has permanent dipoles.
  • ELonger chain , less branched molecules have stronger spontaneous/induced dipoles.
Correct answer: E Longer chain , less branched molecules have stronger spontaneous/induced dipoles.

Full explanation

Boiling points are compared in the following order

– Type of compound (ionic or covalent)

– If covalent, compare the molecular formula

– Then, the polar functional groups and electronegativity

– Shape of the molecule

In the given 2 substances, 2,2 — dimethylpropane, C(CH₃)₄, is an isomer of pentane, CH₃(CH₂)₃CH₃, they have the same molecular formula — same chemical properties. And both are non-polar alkanes. So, the only intermolecular force that can be found is the London dispersion force.

If we compare the shape of the molecules, C(CH₃)₄ is a highly branched structure while CH₃(CH₂)₃CH₃ is fairly straight. Therefore, more surface area in CH₃(CH₂)₃CH₃ leads to stronger dispersion forces (induced dipoles) resulting in higher boiling points.

Therefore, option E best explains the difference in the boiling points for these two substances.

Summary to learn

For molecules with the same molecular formula (isomers) and therefore the same molecular mass, boiling point differences come down entirely to how strong their intermolecular (van der Waals / London dispersion) forces are, which in turn depends on molecular shape: a long, straight-chain molecule has more surface area available for neighbouring molecules to interact with, producing stronger induced-dipole attractions and a higher boiling point, while a compact, highly branched isomer of the same formula has less surface contact and therefore a lower boiling point.

Assume that the oxidation numbers are as shown below:

N = -3 H = +1 Cr = +6 O = -2 Which compound formula given below is correct?

  • A[(NH₄)₂CrO₄]⁺
  • BNH₄Cr₂O₇
  • C(NH₄)₂CrO₄
  • D[(NH₄)₃CrO₄]⁻
  • E(NH₄)₃CrO₄
Correct answer: C (NH₄)₂CrO₄

Full explanation

Oxidation numbers of 4 elements are given :

N = -3 H = +1 Cr = +6 O = -2

Rules of the compound formations are such that if it is a neutral compound, the total oxidation number should be 0. If it is an ionic compound, the total oxidation number should be the same as the oxidation number of the whole compound.

Analysis of the given options

Option A : [(NH₄)₂CrO₄]⁺. 2 NH₄⁺ = +2. CrO₄²⁻ = -2. Total = 0, not +1. Incorrect.

Option B : NH₄Cr₂O₇. NH₄⁺ = +1. Cr₂O₇²⁻ = -2. +1 − 2 = -1, not neutral. Incorrect.

Option C : (NH₄)₂CrO₄. 2 NH₄⁺ = +2. CrO₄²⁻ = -2. +2 − 2 = 0 → neutral. Correct.

Option D : [(NH₄)₃CrO₄]⁻. 3 NH₄⁺ = +3. CrO₄²⁻ = -2. +3 − 2 = +1, not -1. Incorrect.

Option E : (NH₄)₃CrO₄. 3 NH₄⁺ = +3. CrO₄²⁻ = -2. +3 − 2 = +1, not neutral. Incorrect.

Summary to learn

In an ionic compound’s formula, the oxidation numbers of every ion must add up to the compound’s overall charge (zero for a neutral compound, or matching the stated charge for a complex ion) — multiplying each ion’s own oxidation number by however many of that ion appear in the formula. Checking a proposed formula for correctness (or working out an unknown subscript or charge) is simply a matter of doing this weighted sum and comparing it against what the compound’s stated charge requires.

What is the correct formula of propanal?

  • ACH₃CH₂CH₂OH
  • BCH₃CH₂OCH₃
  • CCH₃COCH₃
  • DCH₃CH₂CO₂H
  • ECH₃CH₂CHO
Correct answer: E CH₃CH₂CHO

Full explanation

Propanal is a 3 carbon hydrocarbon with an aldehyde functional group (-CHO).

So, the correct formula is CH₃CH₂CHO

Summary to learn

Simple organic functional groups have distinct name endings and structures: an alcohol (−OH, as in propan-1-ol) ends in “-ol”; an aldehyde (−CHO, always at the end of a carbon chain, as in propanal) ends in “-al”; a ketone (a C=O in the middle of a chain, as in propanone) ends in “-one”; a carboxylic acid (−COOH, as in propanoic acid) ends in “-oic acid”; and an ether (C−O−C linking two carbon chains) is named separately as an “-oxy-” compound rather than with any of these suffixes.

When propan-1-ol is burnt in excess oxygen the only products formed are carbon dioxide and water.

In the balanced equation for this reaction what is the ratio of CO₂ : H₂O molecules formed?

  • A4 : 7
  • B3 : 8
  • C2 : 7
  • D3 : 4
  • E5 : 12
Correct answer: D 3 : 4

Full explanation

Propan-1-ol = C₃H₈O

When propan-1-ol is burnt in excess oxygen, the balanced equation would be:

2C₃H₈O + 9O₂ → 6CO₂ + 8H₂O

From final balanced equation:

6 CO₂ : 8 H₂O

Divide both by 2:

The ratio is 3:4.

Summary to learn

Complete combustion of any hydrocarbon or alcohol in excess oxygen converts every carbon atom in the fuel into CO₂ and every hydrogen atom into H₂O. Writing and balancing that combustion equation for a molecule with a known formula (here C₃H₈O for propan-1-ol) is what gives the exact mole ratio of CO₂ to H₂O produced — three carbons and eight hydrogens per molecule of fuel translate directly into a 3:4 ratio of CO₂ to H₂O once the equation is balanced and simplified.

Potassium nitrate was found to have a solubility of 120 g in 100 g of water at 80 °C and 50 g in 100 g of water at 25 °C.

50 g of water was heated to 80 °C and solid potassium nitrate added until the solution was just saturated.

The solution was then cooled to 25 °C when solid potassium nitrate separated out to leave a saturated solution.

Using the information provided in this question, what is the minimum mass of water that must now be added to the mixture of the solution and the solid in order to make this solid potassium nitrate redissolve at 25 °C?

  • A20 g
  • B140 g
  • C120 g
  • D70 g
  • E190 g
Correct answer: D 70g

Full explanation

Solubility of KNO₃ at 80 °C = 120 g per 100 g water

Solubility at 25 °C = 50 g per 100 g water

We used 50 g of water, heated to 80 °C, and saturated the solution. Then cooled to 25 °C, resulting in solid KNO₃ precipitations. We are to find the minimum mass of water to redissolve the precipitate at 25 °C Amount of KNO₃ dissolved at 80 °C (given : 120 g per 100 g water)

In 50g of water: amount of KNO₃ dissolved = (120 × 50)/(100) = 60g

At 25 °C, the solubility is 50 g per 100 g water.

So in 50 g water, amount of KNO₃ dissolved = (50 × 50)/(100) = 25g

So, at 25°C, only 25 g remains dissolved, and 60−25 = 35 g of KNO₃ precipitates out.

We know:

At 25 °C → 50 g KNO₃ dissolves in 100 g water So, amount of water need to dissolve the precipitate = (35 × 100)/(50 ) = 70g H₂O

Summary to learn

A substance’s solubility — the maximum mass that can stay dissolved in a fixed mass of solvent — generally rises with temperature, so a solution saturated at a higher temperature can hold less dissolved solute once cooled. The mass of solid that comes out of solution (precipitates) on cooling is simply the difference between how much was dissolved at the higher temperature and how much the same water can still hold in solution at the lower temperature; that leftover solid needs additional water to fully redissolve.

Which two of the following oxides would NOT give acidic solutions in water?

CO, CO₂, SO₂, NO

  • ANO and SO₂
  • BNO and CO₂
  • CCO and SO₂
  • DCO and CO₂
  • ECO and NO
Correct answer: E CO and NO

Full explanation

Among the given oxides CO and NO do not form acidic solutions because they do not react with water to release H⁺ ions or form acids.

For CO₂, it reacts readily with water to form carbonic acid (H₂CO₃).

For SO₂, it reacts readily with water to form sulfurous acid (H₂SO₃).

Summary to learn

Whether a nonmetal oxide reacts with water to form an acid comes down to the oxidation state of its central nonmetal atom, and specifically how many oxygen atoms it carries: oxides of carbon and nitrogen at their LOWER, less-oxidised state (like CO and NO) are relatively stable and unreactive toward water, while oxides with more oxygen attached to the same element (like CO₂, SO₂, SO₃, NO₂) readily react with water to form the corresponding acid (carbonic, sulfurous/sulfuric, nitrous/nitric acid).

Which one of the following 0.01 M aqueous solutions has a pH > 7.0?

  • AAlBr₃
  • BNaI
  • CNH₄Cl
  • DNa₂CO₃
  • ECH₃CO₂H
Correct answer: D Na₂CO₃

Full explanation

Analysis of the given options

Option A : AlBr₃

Al³⁺ is a small, highly charged cation — it hydrolyzes water and forms acidic solutions — pH < 7

Option B : NaI Na⁺ is a neutral cation (from a strong base NaOH)

I⁻ is a neutral anion (from a strong acid HI) Neutral solution, pH ≈ 7

Option C : NH₄Cl NH₄⁺ is the conjugate acid of NH₃ (a weak base) → acidic

Cl⁻ is neutral pH < 7 (acidic)

Option D : Na₂CO₃

Na⁺ is neutral

CO₃²⁻ is the conjugate base of HCO₃⁻ (which is a weak acid) pH > 7 (basic)

Option E : CH₃CO₂H

Acetic acid which is a weak acid. So, pH < 7 (acidic)

Summary to learn

Whether a salt’s aqueous solution ends up acidic, neutral or basic depends on the strength of the acid and base that combined to form it. A salt built from a strong acid and a strong base (like NaI, from HI and NaOH) gives a neutral solution, since neither ion reacts with water. A salt whose cation is the conjugate acid of a weak base (like NH₄⁺ from NH₃) hydrolyses to release H⁺ and gives an acidic solution, and a highly charged small metal cation (like Al³⁺) does the same even more strongly. A salt whose anion is the conjugate base of a weak acid (like CO₃²⁻ from HCO₃⁻) instead hydrolyses to release OH⁻, giving a basic (alkaline) solution.

Physics & Mathematics

Mechanics, electricity, thermodynamics, algebra & geometry · 8 questions
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Given that 2 log10(x) − 3 = log10(y). Express y in terms of x.

  • Ay = x²/1000
  • By = 2x/1000
  • Cy = x²/3
  • Dy = x² − 3
  • Ey = 2x/3
Correct answer: A y = x²/1000

Full explanation

We begin with the equation: 2 log10(x) − 3 = log10(y).

Firstly we use the log identity a·log10(x) = log10(xa): 2 log10(x) = log10(x²).

So, log10(x²) − 3 = log10(y). Now, 3 can be written as log10(1000).

So, log10(x²) − log10(1000) = log10(y).

Using the log subtraction identity log10(a) − log10(b) = log10(a/b): log10(x²/1000) = log10(y).

Hence: y = x²/1000.

Hence, the correct answer is (A).

Summary to learn

The three core logarithm identities used constantly in IMAT-style problems are: the power rule, a·log(x) = log(xᴰ); the product rule, log(a) + log(b) = log(ab); and the quotient rule, log(a) − log(b) = log(a/b). Rewriting a plain number as a logarithm (e.g. 3 = log₁₀(1000), since 10³ = 1000) is the key trick that lets a mixed equation of logs and constants be combined into a single logarithm on each side, which can then be dropped entirely once both sides are log(something).

Which one of the following equations is dimensionally consistent (has consistent units)? [All the symbols have their usual meanings: v = velocity; F = force; m = mass; t = time; V = voltage; Q = charge; R₁, R₂, R₃, R₄ = resistance]

  • Aenergy = (½mv²) + Fv
  • Bresistance = R₁ + R₂ + (1/R₃) + (1/R₄)
  • Ctemperature change = energy × m × specific heat capacity
  • Dacceleration = (½vt²) + (F/m)
  • Eelectrical current = (V/R₁) + (Q/t)
Correct answer: E electrical current = (V/R₁) + (Q/t)

Full explanation

Let’s analyze each option.

Option A, energy = ½mv² + Fv: ½mv² has units kg·(m/s)² = kg·m²/s² → Joules. Fv has units (kg·m/s²)(m/s) = kg·m²/s³ → Watts. We can’t add Joules and Watts (power) — inconsistent.

Option B, resistance = R₁ + R₂ + 1/R₃ + 1/R₄: R₁, R₂ are in Ohms, while 1/R₃, 1/R₄ are in 1/Ohms. We can’t add Ohms and 1/Ohms — inconsistent.

Option C, temperature change = energy × m × specific heat capacity: units are J · kg · J/(kg·K) = J²/K, which is the wrong unit for temperature (should be K) — inconsistent.

Option D, acceleration = ½vt² + F/m: ½vt² has units (m/s)·s² = m·s, which is not the unit of acceleration; F/m = (kg·m/s²)/kg = m/s², which is OK. We can’t add m/s² and m·s — inconsistent.

Option E, electrical current = V/R₁ + Q/t: V/R is current (amperes), and Q/t is also current (amperes). Both terms are in amperes — consistent.

Hence, the correct answer is (E).

Summary to learn

An equation is dimensionally consistent only if every term being added or subtracted has exactly the same units, since physically it makes no sense to add, say, energy to power, or resistance to conductance. Checking dimensional consistency means substituting the base SI units for every quantity in each term, simplifying algebraically, and confirming all terms in a sum reduce to the identical unit — a mismatch in even one pair of terms rules the whole equation out, regardless of how physically “reasonable” it might look.

The variables x and y satisfy the following two equations: x + 3y = 13; 2x − y = 5. What is the value of x + y?

  • A7
  • B8
  • C6
  • D9
  • E10
Correct answer: A 7

Full explanation

Given: x + 3y = 13 (1); 2x − y = 5 (2). We have to find x + y.

Firstly, we multiply (1) by 2: 2x + 6y = 26 (3).

Now, we subtract equation (2) from equation (3): (2x + 6y) − (2x − y) = 26 − 5 ⇒ 2x + 6y − 2x + y = 21 ⇒ 7y = 21 ⇒ y = 21/7 = 3.

Now plug into (1): x + 3(3) = 13 ⇒ x + 9 = 13 ⇒ x = 13 − 9 = 4.

So: x + y = 4 + 3 = 7.

Hence, the correct answer is (A).

Summary to learn

Simultaneous linear equations are solved by elimination: multiply one or both equations by a constant so that one variable’s coefficient matches (or is the negative of) its coefficient in the other equation, then add or subtract the two equations so that variable cancels out entirely, leaving a single equation in one unknown to solve directly. Once one variable is known, substituting it back into either original equation solves for the other.

The diagram shows a car of mass 1000 kg travelling at a constant speed of 30 m/s in the direction shown along a flat, level road which forms a circle of radius 50 m.

IMAT 2015 question 56 circular motion diagram

Which row in the table gives both the magnitude of the resultant force on the car and the direction of the acceleration of the car at the instant shown?

RowForceDirection
10 kNR
218 kNQ
318 kNR
430 kNQ
530 kNP
  • Arow 1
  • Brow 2
  • Crow 5
  • Drow 3
  • Erow 4
Correct answer: D row 3 (force 18 kN, direction R)

Full explanation

When the car is undergoing circular motion, there is a net force acting towards the centre of the circle, known as the centripetal force.

As the direction of the force is directed towards the centre, the direction of acceleration is also toward the centre (since acceleration is due to force) — represented here by direction R.

The magnitude of the centripetal force can be calculated using F = mv²/r, where m is the mass of the car, v is its speed, and r is the radius of the circular path.

F = mv²/r = (1000 · 30²)/50 = (1000 · 900)/50 = 18000 N = 18 kN.

Both of these — 18 kN and direction R — are shown correctly in row 3.

Hence, the correct answer is (D).

Summary to learn

An object moving at constant speed along a circular path still accelerates, because its direction of velocity is constantly changing; this centripetal acceleration always points toward the centre of the circle, and the net (resultant) force producing it — the centripetal force — therefore also always points toward the centre, with magnitude F = mv²/r. Even though the object’s speed doesn’t change, its velocity does (since velocity is speed with direction), which is exactly why a net centre-pointing force is needed to keep bending its path into a circle.

The arithmetic mean of the three numbers a, b, c is 8. Find the arithmetic mean of the four numbers: a + 1, b + 2, c + 6, 3.

  • A7
  • B11
  • C5
  • D9
  • E27
Correct answer: D 9

Full explanation

Given: mean of a, b, c = 8, so (a + b + c)/3 = 8 ⇒ a + b + c = 24.

The new numbers are: a + 1, b + 2, c + 6, 3. Their mean is: [(a + 1) + (b + 2) + (c + 6) + 3] / 4.

Simplifying: [a + b + c + 1 + 2 + 6 + 3] / 4. Now substitute a + b + c = 24: (24 + 1 + 2 + 6 + 3) / 4 = 36/4 = 9.

So, the mean of these four new numbers is 9.

Hence, the correct answer is (D).

Summary to learn

The arithmetic mean of a data set is the sum of all its values divided by how many values there are, so if the individual values in a set change by known fixed amounts (or new values are added), the new mean can be found without knowing any individual value: just track how the sum of all values changes, and divide by the new total count of values.

Evaluate: (27² − 23²) + (14² − 6²)

  • A1680
  • B360
  • C80
  • D840
  • E40
Correct answer: B 360

Full explanation

We have to evaluate (27² − 23²) + (14² − 6²). Use the identity a² − b² = (a − b)(a + b).

27² − 23² = (27 − 23)(27 + 23) = 4 · 50 = 200.

14² − 6² = (14 − 6)(14 + 6) = 8 · 20 = 160.

Sum: 200 + 160 = 360.

Hence, the correct answer is (B).

Summary to learn

The difference-of-two-squares identity, a² − b² = (a − b)(a + b), turns a hard-to-compute subtraction of two large squared numbers into a quick multiplication of two much smaller numbers, since (a − b) is usually small when a and b are close together. Recognising this pattern in an arithmetic expression is often far faster than computing each square directly and then subtracting.

An aluminium block of mass 2.5 kg is supplied with 9000 J of thermal energy. This causes its temperature to rise by 4 K. Which expression gives the specific heat capacity of this aluminium, from this data? [Assume that the block remains solid throughout, and that no additional energy is exchanged between the block and the surroundings.]

  • A9000 × 2.5 × 4 J kg−1K−1
  • B(2.5 × 4)/9000 J kg−1K−1
  • C(9000 × 2.5)/4 J kg−1K−1
  • D9000/(2.5 × 4) J kg−1K−1
  • E(9000 × 4)/2.5 J kg−1K−1
Correct answer: D 9000/(2.5 × 4) J kg−1K−1

Full explanation

Thermal energy supplied Q = 9000 J. Mass of aluminium block m = 2.5 kg. Temperature change ΔT = 4 K.

We need an expression for specific heat capacity: Q = mcΔT ⇒ c = Q/(mΔT).

Substituting values: c = 9000/(2.5 · 4) = 9000/10 = 900 J/(kg·K).

So the expression is: c = 9000/(2.5 × 4) J kg−1K−1.

Hence, the correct answer is (D).

Summary to learn

Specific heat capacity relates the thermal energy supplied to a substance’s resulting mass and temperature change through Q = mcΔT, so rearranging for c gives c = Q ÷ (mΔT) — energy supplied, divided by the product of mass and temperature change. Any question asking for “the expression for specific heat capacity” from given data is really just asking for this rearranged formula with the specific numbers substituted in, not for the final calculated numeric value itself.

Two forces F of equal magnitude act on a beam of length d. Which diagram shows a couple acting, and correctly states the magnitude of the torque (moment) of the couple about the pivot? [The pivot is at the centre of the beam.]

  • ADiagram: force F acts upward at the left end, force F acts downward at the right end (opposite directions, offset from the pivot) — labelled torque = (F × d)/2
  • BDiagram: force F acts leftward at the left end, force F acts rightward at the right end, both forces in line with the beam itself (not offset) — labelled torque = F × d
  • CDiagram: force F acts upward at the left end AND upward at the right end (same direction, not opposite) — labelled torque = F × d
  • DDiagram: force F acts upward at the left end AND upward at the right end (same direction, not opposite) — labelled torque = (F × d)/2
  • EDiagram: force F acts upward at the left end, force F acts downward at the right end (opposite directions, offset from the pivot) — labelled torque = F × d
Correct answer: E Diagram with two equal, opposite, offset forces F, labelled torque = F × d

Full explanation

A couple is two equal and opposite forces acting at different points, producing rotation. The forces are equal in magnitude and are always anti-parallel (i.e. they act in opposite directions along the same or parallel lines of action).

Torque of a couple = force × perpendicular distance between the lines of action.

Look for a diagram with: two equal, opposite forces, acting on opposite sides of the pivot (centre), not in line with each other. These conditions are shown correctly in the diagrams of options A and E.

As the distance between the forces is d, and each force is F, the torque of the couple is: Torque = F × d.

Option A shows the right diagram but the wrong formula (F×d/2, not F×d), so option E — with the correct diagram AND the correct formula — is the right answer.

Hence, the correct answer is (E).

Summary to learn

A couple is a special pair of forces: equal in magnitude, opposite in direction, and acting along two separate (non-overlapping) parallel lines of action, which together produce pure rotation with no net translational force. The turning effect (torque or moment) of a couple is calculated as Torque = one force’s magnitude × the perpendicular distance between the two lines of action — not divided by two, since both forces contribute their full turning effect around any point between them.

Frequently Asked Questions

Right here — every question from the IMAT 2015 exam (General Knowledge, Logical Reasoning, Biology, Chemistry, Physics and Mathematics) is solved and explained on this page, for free, with no sign-up required.

Yes. Every calculation, chemical and biological fact was independently re-derived and checked by the LOCOMOTIVE academic team before publishing.

The IMAT is a single 100-minute test made up of General Knowledge & Logical Reasoning, Biology, Chemistry, Physics & Mathematics questions. Correct answers score +1.5, unanswered questions score 0, and incorrect answers score −0.4 (the exact weighting has varied slightly by year — always check the official rules for the year you are sitting).

The overall syllabus (General Knowledge, Logical Reasoning, Biology, Chemistry, Physics & Maths) has stayed broadly the same, but the exact number of questions, section weighting and question style have changed over the years — this 2015 paper is a great way to build core knowledge, but always pair it with recent past papers to get used to the current format.

Yes — the underlying subject knowledge and reasoning skills are directly transferable, which makes older papers like this one useful extra practice once you’ve worked through the most recent papers.

Looking for more practice? Browse all IMAT Past Papers on LOCOMOTIVE.

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