Tiny GMAT Critical Reasoning Mistakes You Might be Making (Part 1)


Manhattan Prep GMAT Blog - Tiny GMAT Critical Reasoning Mistakes You Might be Making (Part 1) by Reed ArnoldGuess what? 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.

Critical Reasoning. It’s not the easiest subject to teach, I tell ya. Or to study. On the one hand, it’s deceptively simple: ‘here are four sentences, answer a question about them.’ You might be glad there are no formulas, no little rules to memorize. Unlike geometry, in which you might not see a 5-12-13 triangle on the actual test but need to know about them just in case, GMAT Critical Reasoning is usually just a game of spotting a few parts of an argument and answering the question logically.

But while there are certain things that show up again and again—premise, conclusion, counterpoints, assumptions—there are a lot of different ways the GMAT can construct the logic, and a lot of different ways they can make wrong answers seem tempting. How many times have you been wrong but the answer just felt so right?

The fact is, just like there are little rules of geometry you need to be aware of even though you might see them on test day, there are little rules in Critical Reasoning you need to know as well. So I’ve been putting myself on the lookout for them, with the ultimate goal of having a list of Critical Reasoning rules just like you might have a list of Quant formulas (remember: memorizing the list is only step one; training your mind to recognize when to apply those rules is the main challenge).

What follows are three tiny GMAT Critical Reasoning mistakes you want to be aware of. For each, I’ve written an argument of my own and asked a question with two possible answers—one correct, one that is a wrong answer with the flaw highlighted by the section. At the end of the section I’ll point you to a real CR problem in the Official Guide that has the same issue. Do that CR problem, and try to identify not just the right answer, but the answer that has this flaw. I’ll explain those flaws at the end.

What is the tiny flaw in the wrong answer choice?

1) It Talks about Amount When the Argument is Binary

People aren’t even aware of the amount of time they spend on their phones. Logitech has a feature that detects when your eyes are on the phone screen and a timer that keeps track of how long you’re looking at your screen during a 24 hour period. They predict that the technology will cause people to spend less time scrolling mindlessly and wasting time on their phones.

Which of the following, if true, most weakens the argument?

A) Some people have noticed the detection system causes the timer to count when people’s eyes are looking near, but not directly at, their screen.

B) Studies have shown that when people are reminded how much time they spend reinforcing bad habits, they only reduce the time spent on those habits by a few minutes.

‘Oh, perfect, well if it only causes people to cut back a few minutes, it pretty much seems like my argument is debunked.’

Hold up. What was my conclusion? Specifically, word for word. It says that the technology will cause people to spend less time on their phone. It never once specified how extreme the results would be—only that there would be results. In order to weaken, I need to show that people might not spend less time on their phone. Statement A gives people a reason to doubt the timer, so they might not spend less time overall looking at their phones.

Statement B is written like a weakener, and boy does it sound like one. But it’s actually a strengthener! It gives reason to believe people will cut back on phone-time, even if only a little bit.

In real life, it’s something you’d do all the time. If someone told you that with only fourteen weeks of working out at 3 a.m. you could lose weight, and you found out that that weight was 3/8 of a pound, you’d probably say, “No thanks, crazy dude, I’ll sleep in and suffer the hint of a trace of the possibility of a love handle.”

But technically, 3 a.m. gym bro’s argument wasn’t wrong. You would lose weight.

Look out for this. I often tell my students, “Unless rank is mentioned, rank doesn’t matter!” How big/small/much/little something is doesn’t change whether or not it’s there in the first place. If the argument is about existence, don’t make it about size. Because in that case, size doesn’t matter.

…I mostly just wonder if that sentence makes it past the censors.

(Real OG Example: page 534, CR 628 about Beach City Airport)

2) It Conflates the Meaning of Two Related but Actually Different Ideas

In order to get into a music festival, it is required that everybody purchase a ticket ahead of time. When the ticket is shown at the gate, a bracelet is put on a person’s right wrist. This was done so that it would be easy for security to see people who snuck into the festival and easily remove them.

Which of the following most weakens the argument?

A) After complaints last year from people who had trouble taking off the bracelets after the festival, the bracelet this year was made to be more easily removed.

B) A similar looking bracelet can be constructed out of construction paper and spit.

‘…These both seem right.’

They’re not.

‘You’re positive?’

Pretty positive.

‘I feel like they both make the argument weaker. One gives me reason to believe security will throw out people that didn’t sneak in but who lost their bracelet, the other that the bracelet is easy to fake.’

You have to pick.

‘Ugh. Fine. If the bracelet is easily removable, then it might fall off, so, I guess, A.’

Final answer?

‘I got it wrong, didn’t I.’



Stop it.

You’ve conflated two related but different meanings (two, really): making a bracelet more easily removable, as the argument said, is different than being easily removed. Not only that, being easily removed is not the same thing as easily falls off.

GMAT texts need to be read very literally and very specifically. Words mean exactly what they mean, and you’re not allowed to make connections from your own assumptions, usually based on ‘real world stuff.’ You’re not in the real world; you’re in GMAT world. Different rules apply.  

There’s a difference between attending and graduating a school, buying a ticket for and actually seeing a movie, or acting and whatever Aidan Gillen claims to do. Don’t conflate the two if the passage doesn’t allow them equivalence. These wrong answer choices are often hastily explained as being ‘out of scope.’ Well, sure, but you should specify and understand exactly why an answer is out of scope and, more importantly, why it is tempting even though it’s out of scope. Often it’s because the GMAT brings in these related—but distinct—ideas.

(Real OG Example: page 542, CR 656 about fire alarms and prank calls)

3) It Provides Explanations for the Premises

Steve and Bill need to purchase several computers to get the ball rolling on their tech startup. It will be a costly endeavor, but they have a decent amount of money saved between them, so it’s likely that they’ll be able to get started by the end of the year.

Which of the following, if true, strengthens my argument?

A) Steve won 100,000 dollars in the lottery earlier this year.

B) Bill and Steve paid off student loans five years ago.

I suspect that even if you ended up getting this correct, for a hot second, you were in love with answer choice A. “Oh, fantastic, I need it to be likely they’ll be able to start this tech company soon, and then, here’s Steve, the lucky jerk, winning the lottery. The argument is definitely stronger since he can use those 100Gs to purchase some computers, and he’ll probably have enough money to go on vacation, too. Man, I hate that guy.”

It’s very, very tempting. But also very, very wrong.

‘How?! They need money! I’m told he won 100,000 dollars!’

But read the problem carefully. What does the lottery win really do to my argument? I’m already told they have money saved, so they’ll be able to start the company soon. All statement A does is tell me where some of that money came from. It explains a premise. Explanations of the premise don’t help my argument. The premises are to be accepted as true; I don’t need to find something that gives them more detail or explains how they came to be. What I really need for this argument to work is to know that the guys are willing and able to spend the money they’ve saved—however they accrued it in the first place—to start their company. Statement B lets me know that they won’t be spending money paying for some other very expensive thing and thus are more likely to be able to afford what they need for the company.

‘I hate you.’

I know, I’m very sorry. But look out for this: answers that seek to explain the circumstances but don’t add anything to the argument itself.

(Real OG Example: page 540, CR 647, a tragic passage about sea otter decline)

There’s three for now. I’ll be keeping my eye out for others; you should do the same. When you get a GMAT Critical Reasoning question wrong that you’re just certain is right, really dig in and specify why you missed it. Make a flashcard to remind you of this faulty logic, and try to start noticing it in answer choices for other passages. Let us know if you make any discoveries, and go on to Part 2 for even more tiny GMAT Critical Reasoning mistakes.


Example 1, CR 628: C is wrong because it brings in a quantity that isn’t relevant to the argument. C suggests that “the people who won’t be coming will be the high spenders,” but the argument never depended on losing low spenders or losing high spenders—just on losing spenders. Even if only one fewer tourist came, that’s money the city isn’t receiving, and thus, a loss of revenue.

Example 2, CR 656: Answer choice C conflates some ideas here. It’s tempting! “This sounds good for fire fighters—seems like it strengthens my argument!”—but the argument is about people’s ability to report a fire. Now, typically fire fighters fight fires after a report has been made, but the two are, in the end, different things. (Similarly, answer choice E might be tempting—but public telephones aren’t the same thing as fire alarm boxes in public!)

Example 3, CR 647: Answer choice E might be tempting. After all, if the seal food supply goes down, the seal population goes down, and when there are fewer seals, the whales eat otters. But notice—the argument already tells us the seal population has been low. E just offers a possible explanation for why this might have happened.

Happy studying! 📝

Want some more GMAT tips from Reed? Attend the first session of one of his upcoming GMAT courses absolutely free, no strings attached. Seriously.

Reed Arnold is a Manhattan Prep instructor based in New York, NY. He has a B.A. in economics, philosophy, and mathematics and an M.S. in commerce, both from the University of Virginia. He enjoys writing, acting, Chipotle burritos, and teaching the GMAT. Check out Reed’s upcoming GMAT courses here.

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