Top 10 Tips for GMAT Critical Reasoning


Manhattan Prep GMAT Blog - Top 10 Tips for GMAT Critical Reasoning by Chelsey Cooley

Feeling stumped by GMAT Critical Reasoning? Here are our 10 best GMAT Critical Reasoning tips. You’ll find tips for studying Critical Reasoning before test day, as well as maximizing your chances of getting tough questions right.

1. Don’t start at the beginning.

A normal GMAT Critical Reasoning argument contains a conclusion and premises that support the conclusion. However, there are a couple of unusual problem types (Draw a Conclusion and Explain the Discrepancy) where this doesn’t apply. Draw a Conclusion problems don’t have a conclusion at all!

The only way to tell what problem type you’re solving is to read the question, which always appears beneath the argument. Always read the question first. That’s how you’ll know whether you’re about to read a normal argument or something weird. If you don’t do this, you can waste time looking for a conclusion that isn’t even there.

For more on the different GMAT Critical Reasoning problem types, check out this article by expert instructor Stacey Koprince.

2. Why do you believe that, anyways?

Here’s a way to really understand a GMAT Critical Reasoning argument. First, spot the conclusion of the argument. Then, ask yourself this question:

“Why does the author believe that, anyways?”

Most GMAT Critical Reasoning problems don’t ask you to just point to the premises and the conclusion. You need to understand the author’s reasoning and how it supports their claim. Here’s an example:

“It often costs much less in the long run to lease a car than to buy a comparable one. If you own a car, it depreciates in value over time. A monthly lease payment can also be as little as half the amount of a loan payment for the same car.”  

The conclusion is in the first sentence. The second two sentences are premises, but you shouldn’t stop there. Instead, break down the author’s reasoning until you understand why she believes her conclusion. Here are her premises:

  • A car you own depreciates over time
  • If you lease a car, you might pay half as much per month as you would if you purchased one

But how do those premises connect to her belief?

  • A car that you own depreciates over time. She must be assuming that a car that you lease doesn’t depreciate over time, so that when you compare owning versus leasing, the loss to depreciation is lower. Plus, she’s thinking that the depreciation issue is big enough that it tips the scales in favor of leasing, rather than owning.
  • If you lease a car, your monthly payments might be half as much. Why would this make a leased car less expensive? That would only be true if you paid for the leased car for the same number of months as the car you owned. Also, the lower payments couldn’t be outweighed by other costs.

Once you start really questioning how the premises connect to the conclusion, you’ll start to spot assumptions that aren’t necessarily true. A lower monthly payment doesn’t mean that something is less expensive, after all. But that’s what the author thinks, so it’s a critical part of the argument!

3. Get weird on GMAT Critical Reasoning

A lot of Critical Reasoning problems ask you to find holes in an argument. A good way to do this is by thinking of strange and extreme scenarios and asking whether the argument would still make sense.  

Let’s look at that argument about car leases again.

“It often costs much less in the long run to lease a car than to buy a comparable one. If you own a car, it depreciates in value over time. A monthly lease payment can also be as low as half the amount of a loan payment for the same car.”  

Take the first premise, about depreciation, and picture a weird scenario related to it.   

  • What if cars only depreciated in value by 0.001% per year?

Take that strange possibility, and use it to poke a hole in the argument! If the amount of depreciation is tiny, then you can’t argue that a leased car will cost “much less.” Therefore, the author is assuming that the depreciation is significant.

Try the same approach with the second premise.

  • What if all car loans only lasted a single year, while leases all lasted ten years or more?

Sure, the monthly payment would be much lower for a lease, but in the long run, you’d save money by buying a car.

4. Look for places to drive a wedge in.

The weakest parts of an argument are its strongest claims. Which of these claims is less likely to be correct?  

  • “All cases of diabetes are caused by excessive sugar intake.”
  • “Excessive sugar intake can cause diabetes.”

How about this pair? Which statement is less likely to be right?  

  • “If we launch a new marketing campaign, our company’s revenue will be higher in 2019 than it was in 2018.”
  • “We should launch a new marketing campaign this year.”

And this one?

  • “The recently discovered novel could not have been written by Smith.”
  • “The recently discovered novel was more likely to be written by Jones than by Smith.”

In each pair, the first statement is less likely to be right than the second one. That’s because the first statement makes a stronger, bolder claim. In the words of the late Carl Sagan, “extraordinary claims require extraordinary evidence.” Without extraordinary evidence (a study of every single diabetic person in the world), it would be extremely hard to prove that all diabetes is caused by sugar.

When you do Critical Reasoning problems, you should read arguments skeptically. Look for ways in which the argument could be wrong. One of the best places to find issues with an argument is by attacking the strongest claims it makes. If you see strong language, such as “all,” “every,” “cannot,” “never,” etc., you can probably think of a counterexample.

5. Spot the modifiers.

Modifiers? These are supposed to be GMAT Critical Reasoning Tips, not GMAT Sentence Correction tips, right? But modifiers can actually help you with GMAT Critical Reasoning. Here’s an example:

The patio is wet. Therefore, it must have rained last night.

There’s a modifier in the conclusion: the phrase last night. When you see a modifier in the conclusion, zero in on it and see if it points you to a flaw in the argument. In this case, what if it rained this morning, or two days ago, instead of specifically last night?

How about this one?

Bicycle helmets cause an 85% reduction in the frequency of cycling-related injuries to the head and face. The province of Malvernia hopes to prevent a significant fraction of cycling injuries by mandating helmet use for everyone under the age of 12, starting this year.

Now, we have three modifiers. One is in a premise: to the head and face. The others are in the conclusion: for everyone under the age of 12 and starting this year. Be skeptical of both of these! What if there are currently almost no head and face injuries? Reducing them by 85% would be good, but it wouldn’t prevent a significant fraction of all injuries. And where did the people under age 12 come from? It’s possible that head and face injuries primarily, or solely, affect older cyclists. Finally, “starting this year?” What if everybody is already wearing a helmet right now?

6. Don’t be fooled by sketchy math.

GMAT Critical Reasoning loves to confuse you with percents, numbers, rates, and relationships. Critical Reasoning might not be on the Quant section, but a little math awareness still helps! Here are some concepts to be careful with:

  • Overall cost versus cost per unit
  • Number of people versus percent of people
  • Rate per 1000 versus total number
  • An increasing number versus a high number

Here are two bad arguments that you might see, based on these ideas. Can you find some flaws in each of these?

  • Switching from using unobtanium to using kryptonite in our microprocessors will reduce the cost of producing each ZPhone by 15%. If we make the switch, our profits should increase.
  • In Springfield County, 1 in 4 deaths is attributable to heart disease, while in Winston County, heart disease only accounts for 1 in 12 deaths. Winston County should not receive as much funding for heart disease treatment programs as Springfield County.

7. Some arguments “tell you why.”

A lot of GMAT Critical Reasoning arguments talk about why something happened. According to data from GMAT Navigator, this type of argument shows up a lot in really tough Critical Reasoning problems. Here’s what it might look like:

“Joel showed up to work this morning in a brand new Lamborghini. He probably won the lottery.”

The conclusion is that Joel won the lottery. It’s trying to explain why he’s driving a Lamborghini! Some arguments also make assumptions about why something happened:

“I’ve been sick all week. I should stop going outside when it’s raining.”

In this argument, the author doesn’t directly explain why she’s been sick. But she implies that she’s been sick because she’s been going outside in the rain. Let’s see one more:

“There were strange lights in the sky over Seattle last night. We were probably visited by UFOs.”

This type of argument often shows up in tricky Weaken the Argument problems. One way to weaken this type of argument is to show that there might have been another reason for whatever happened. If there’s a different possible explanation—swamp gas instead of UFOs, for instance—then the explanation in the argument might be wrong.

Try thinking of good weakeners for the first two arguments, about the Lamborghini and the week-long illness. Here are ours:

Weakener: “This afternoon, I saw Joel on the news, being arrested for car theft.”

Weakener: “I work in a daycare and every child there has been sick for two weeks.”

8. Boring is beautiful… but not always.

In this article, GMAT instructor Ryan Jacobs explains why you shouldn’t cross off “weird” Critical Reasoning answers. Here’s the rundown on answer choices that look weird. In some problem types, the most boring-looking answer is often the right one. (By “boring,” we’re talking about anything that just reuses ideas and language from the argument, rather than introducing a new idea.)

In other problem types, “exciting” answers are more likely to be right. An “exciting” answer is one that tells you something brand-new that wasn’t addressed in the argument. Here’s the breakdown:

Boring answers are usually right in Find the Assumption problems and Draw a Conclusion problems.

Exciting answers are usually right in Strengthen/Weaken/Evaluate the Argument problems and Explain the Discrepancy problems.

Why? Find the Assumption and Draw a Conclusion are all about using the information you’ve been given. You’re not allowed to add in any new facts. In these problems, the right answer often looks dull and wishy-washy.

In the other problem types, new information is good! You’re specifically trying to add in a new fact that will impact the argument. An answer choice that seems to come out of nowhere could be right.

Here’s more reading material about boring answers on GMAT Verbal.

9. What if you’re stuck between two answers?

Ever catch yourself crossing off an answer choice just because you were sick of looking at it? Because it sounded weird or didn’t make sense to you? Because you couldn’t figure out what it was saying? We all do this, but it’s not a good move.

In hard GMAT Critical Reasoning problems, the GMAT writers want the right answers to look off-putting and strange. After all, the hard problems are hard because most people don’t pick the right answer! If you eliminate something just because it looks weird, you might have just crossed off the right answer.

Where does the “stuck between two” problem come into it? The next time you get stuck between two answer choices, take a second look at those answers. You probably aren’t stuck because they both sounded great! More likely, they both sounded pretty lousy. Usually, one of them was an answer that you didn’t really understand. The other was an answer that made sense but that you weren’t totally satisfied with. You were dealing with a wrong versus weird scenario.

This article by GMAT instructor James Brock gives you the details on wrong versus weird. The quick tip, though, is to pick the weird answer, not the wrong answer. If you know an answer is wrong, cross it off, even if the other answer doesn’t make a lot of sense! It’s okay to pick an answer you don’t totally get, as long as you eliminated everything else.

10. Know yourself.

First of all, keep an error log for Critical Reasoning—even if it seems hard or pointless at first! Here’s why it’ll pay off. You can use your Critical Reasoning error log as an opportunity to understand yourself better.

Every time you eliminate an answer or pick an answer, you had some kind of reason for it. Some of those reasons will be good ones (you thought through the logic and picked the answer that seemed to follow the rules). Other reasons won’t be so good. They might even make you feel silly when you think back to them. Here are some common “silly” reasons to cross off an answer:

  • It talked about something that wasn’t in the problem.
  • It seemed too long.
  • It had a lot of weird language or jargon in it.
  • I didn’t know what it meant.
  • It used a particular phrase that seemed weird to me.
  • I didn’t actually read it! I got too hung up on an earlier answer and totally skipped this one.
  • I read it, but I went too quickly and missed a keyword.

Every time you get a Critical Reasoning problem wrong, dig into why you eliminated the right answer (even if you did it for a silly reason). Also, think about why you chose the wrong answer. You might have had a logical reason for it, in which case you should reflect on your logic and see if you can figure out what went wrong! Or, it might have been a “silly” reason too.

The point of keeping a Critical Reasoning error log isn’t to beat yourself up over mistakes, or to record every detail of the correct solution. It’s to find patterns in how you think and how you act that you might not have noticed otherwise. Knowing yourself is the first step to being a smarter, stronger, faster GMAT taker. 📝

Want more guidance from our GMAT gurus? You can attend the first session of any of our online or in-person GMAT courses absolutely free! We’re not kidding. Check out our upcoming courses here.

Chelsey CooleyChelsey Cooley Manhattan Prep GRE Instructor is a Manhattan Prep instructor based in Seattle, Washington. Chelsey always followed her heart when it came to her education. Luckily, her heart led her straight to the perfect background for GMAT and GRE teaching: she has undergraduate degrees in mathematics and history, a master’s degree in linguistics, a 790 on the GMAT, and a perfect 170/170 on the GRE. Check out Chelsey’s upcoming GMAT prep offerings here.

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