Assumptions are one of the most important parts of the critical reasoning section on the GMAT. But what really are assumptions? In a nutshell, assumptions are things taken for granted.
We take many things for granted in life, more than we realize. For example:
Anish says there are 25 girls at the bar in Buenos Aires. By believing him, I am assuming several things:
- Anish knows what he is talking about.
- Anish can count to 25.
- Anish is telling the truth.
If any of the above assumptions were not true, it wouldn’t make much sense to believe Anish:
- Why would I believe someone who doesn’t know what he is talking about?
- Why would I believe someone who can’t count to 25 if he says anything involving the number 25?
- Why would I believe someone who is lying?
Basically, detecting assumptions helps us become skeptics who think twice before accepting a flawless argument with a shaky foundation, which in the world of business could mean switching the Anish bar example to someone advising that we should invest in a certain company. In this case, the ramifications of making the wrong assumptions could be much worse than spending a night at a sausage fest.
Assumptions on the GMAT may not be quite as simple, but once we get a good grasp of what an assumption really is, it becomes much easier to detect them on the GMAT. So without further ado, let’s look at how I personally approach assumption problems on the GMAT (I stress it is how I do this because there isn´t a single right way to approach these, this is just the one that works for me) .
Investigators concluded that human failure was not responsible for the fatal airplane crash last August, and since that time new and more stringent rules for identifying and reporting mechanical problems have been in effect. That accounts for the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August.
Which one of the following is an assumption underlying the argument in the passage?
- (A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems.
- (B) Mechanical problems in airplanes have increased dramatically since last August.
- (C) Mechanical problems in airplanes have not increased by 50 percent since last August.
- (D) Airlines are less reluctant to report mechanical problems than they previously were.
- (E) Mechanical problems in airplanes have become easier to detect since last August.
So how do I go about answering this question? First thing is to ignore all the BS, and simplify the problem:
Premise – Reports of mechanical problems have gone up 50%
Conclusion – The cause for the increase are the more stringent rules for reporting incidences.
Question – Which assumption makes this conclusion true? Or, which assumption helps eliminate other conclusions?
Let´s look at the answer choices, and see which one makes the most sense:
- (A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems. The conclusion says nothing about the safety of airplane travel – Irrelevant
- (B) Mechanical problems in airplanes have increased dramatically since last August. This one is relevant, but an increase in problems would be a direct explanation for why the reports increased, therefore negating the argument.
- (C) Mechanical problems in airplanes have not increased by 50 percent since last August. In analyzing answer B we established that an increase in problems is another possible explanation for the increase in reports, by ASSUMING that an increase in problems is not the explanation, we are strengthening the original conclusion. This answer makes sense, but I still wouldn´t commit to it, have to continue analyzing all of the answers just in case.
- (D) Airlines are less reluctant to report mechanical problems than they previously were. Same problem as B
- (E) Mechanical problems in airplanes have become easier to detect since last August. Same problem as B and D.
Correct answer is C
A recent study has concluded that, contrary to the claim of those trying to ban cigarette advertisements altogether, cigarette ads placed on billboards and in magazines have little to no effect on the smoking habits of the smokers who views the ads. The study, which surveyed more than 20,000 smokers and solicited their reasons for continuing to smoke, found that practically no one in the survey felt that these advertisements influenced their decision to smoke.
The study’s conclusion is based upon which of the following assumptions?
- (A) People do not switch cigarette brands based on their exposure to cigarette ads on bill boards and in magazines.
- (B) Cigarette ads on billboards and in magazines do not encourage non smokers to take up the habit.
- (C) Banning cigarette ads altogether will encourage people to give up smoking.
- (D) people are consciously aware of all reasons they choose to smoke.
- (E) People who decide to smoke do so for rational reasons.
This question has a lot of fluff that isn’t saying much at all, so let’s do the same as last question and summarize the question:
Premise – Some (ignore the numbers when structuring the question, 20,000 in this case, as they are only there to confuse) smokers said that cigarette ads in magazines and billboards had no impact on their smoking.
Conclusion – Therefore these ads have little to no effect on the habits of smokers who view the ad.
Question – What assumption makes this conclusion true?
This argument seems fairly straight forward, they said this, therefore this is true. If you remember the Anish example of him saying there are 25 girls at the bar, one assumption is that he knows what he is talking about. This argument assumes that these 20,000 people know WTF they are talking about:
- (A) People do not switch cigarette brands based on their exposure to cigarette ads on billboards and in magazines. Argument says nothing about brands or switching them – Irrelevant.
- (B) Cigarette ads on billboards and in magazines do not encourage non smokers to take up the habit. Argument specifically talks about the effect it has on smokers, not nonsmokers – Irrelevant.
- (C) Banning cigarette ads altogether will encourage people to give up smoking. Helps the opposite point of view of the argument, so can´t be an assumption of the argument.
- (D) People are consciously aware of all reasons they choose to smoke. AKA – They Know what they are talking about – this is the right answer.
- (E) People who decide to smoke do so for rational reasons. Irrelevant.
Correct answer is D
Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year’s total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year’s number.
Which of the following is required for the revamped collection program to achieve its aim?
- (A) This year, no materials that city services could separate for recycling will be incinerated.
- (B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
- (C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
- (D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
- (E) The total quantity of refuse collected by Shelbyville city services this year will be no greater than that collected last year.
This is a tougher question than the other two, but let´s go through the same process of reading through the BS:
- All refuse collected last year in Shelbyville was incinerated.
- Through recycling, Shelbyville will reduce the number of truckloads of refuse for incineration to half of last year´s number (This is important, and helps eliminate 2 wrong answers. One of the key phrases we have to pay attention to when reading the question).
- The goal for the program is to cut residual ash in half.
Question: What is a requirement for the initiative to reach its aim?
Unlike the other questions, this passage does not have a conclusion. If it makes things easier, we can make up a conclusion that goes with the question: The initiative will achieve its aim.
Let´s go through the answers:
- (A) This year, no materials that city services could separate for recycling will be incinerated. Tempting…But not definitive, come back later. I will go see if there is any other valid answer before spending too much time analyzing it.
- (B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash. Cost is irrelevant.
- (C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year. The passage gives us the final number for the amount of garbage to be incinerated compared to last year (the part I highlighted in the summary), so it is irrelevant.
- (D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year. If the refuse incinerated this year generated more ash per truckload when compared to last year’s refuse, then the plan will not achieve the goal – answer is correct.
- (E) The total quantity of refuse collected by Shelbyville city service’s this year will be no greater than that collected last year. Like C, the amount of refuse to be incinerated as compared to last year is already given by the highlighted portion – Irrelevant.
Going back to A, a couple of things come to mind:
- D is much stronger
- One clue of why it is not the answer is the word could. The question is talking definitively about what will and will not be recycled, the word “could” does not belong in this question. This is a very interesting lesson, as the test gives these subtle clues on most difficult questions, and it is up to us to detect them.
Correct answer is D
So, this is how I approach these critical reasoning GMAT problems . If there are any simple lessons to take from this, they are:
- Ignore the BS
- Question everything
- Look for subtle GMAT clues
I hope this was helpful to at least some of you, and if you have any questions or feedback please do not hesitate to get in touch with Anish or myself and we will be happy to help, although it is up to you to decide whether we know what we are talking about…