GMAT Questions and Critical Thinking: Improve Your Timing

GMAT questions are typically designed so that you can get to the correct answer with more than one approach. In that way, the GMAT rewards critical thinking. While the long, step-heavy, technical approach can get you to the correct answer, it’s likely that there is a much faster, strategic approach that will save you time, requires less effort and helps you avoid overall pacing problems (so that you don’t have to guess on a bunch of questions at the end of the section because you’re low on time).

When you consider the following quant question, which approach immediately comes to mind? Is ‘your way’ of approaching this question actually the fastest way? Consider the four methods of approach below…

If Jake loses eight pounds, he will weigh twice as much as his sister. Together they now weigh 278 pounds. What is Jake’s present weight, in pounds?

a)    131

b)    135

c)    139

d)    147

e)    188

After looking at this prompt, many GMATers will be reminded of algebra that they’ve done before. There are actually two different ways to do that algebra though:

1) Algebra with two variables

Let’s call the two variables ‘J’ (for Jake’s present weight) and ‘S’ (for the sister’s present weight). Based on the information in the prompt, we can create two equations:

(J – 8) = 2(S)

J + S = 278

From here, you can use ‘substitution’ to solve for J…

S = 278 – J

(J-8) = 2(278 – J)

J = 556 – 2J + 8

3J = 564

J = 188

This is pretty straightforward algebra, but it’s arguably the approach that takes the longest on this GMAT question.

2) Algebra with one variable

We can use the variable ‘J’ to represent both weights…

J = Jake’s present weight

(J-8)/2 = Sister’s present weight

Since the combined weight of the two people is 278 pounds, we can create an equation to account for all of this information:

J + (J-8)/2 = 278

2J + (J-8) = 556

3J – 8 = 556

3J = 564

J = 188

This approach may or may not be faster for you with regards to this particular GMAT question, but it’s definitely something to consider.

3) Test the answers

Since the answers to most quant questions are numbers, and we’re asked to find Jake’s present weight when accounting for a couple of pieces of information, we can use the answers to our advantage and find the one that ‘fits’.

Since Jake weighs more than his sister, let’s test one of the larger numbers. If we start with answer ‘D’ (147 pounds), we would end up with the following:

After losing eight pounds, he would weigh twice what his sister weighs:

147 – 8 = 139

139/2 = 69.6

However, when you add up these two weights (147 and 69.6) you end up with a total of 216.5 pounds. We were told that they weigh a total of 278 pounds though. These two values combined are therefore too small; both Jake and his sister have to weigh more than this. There’s only one answer that is greater than ‘D’, so that must be the correct one.

By doing a little arithmetic and proving that answer ‘D’ was too small, we were able to find the correct answer to this quant question. This is far less effort than either of the first two options.

4) Logic and critical thinking

Based on the information in the prompt, we can deduce that Jake currently weighs more than twice his sister. By employing some critical thinking, we know that with a combined weight of 278 pounds, Jake’s weight has to make up most of that total (which means that he has to weigh a lot more than half of the 278 pounds total). Take a good look at the five answer choices. Two of them are actually less than half the weight, one is exactly half the weight and one is just a little more than half the weight. Logically, the only answer that makes sense is ‘188’.

Even if you want to take the time to double-check this work, you’ll see that 188 + (188-8)/2 = 188 + 90 = 278. This method is arguably just as fast as the third option, and both were faster than the first two, algebra-step-heavy, options.

The takeaway

When training for the GMAT, which tests critical thinking heavily, you should be looking to improve in all areas - not just in terms of content, but also the powerful tactical aspects of training for the exam. Additionally, avoid the temptation to solely review the areas in which you’re getting questions wrong. If you ignore the questions that you’ve answered correctly, then you might be missing out on learning ways to significantly increase your GMAT score.