Tiny GMAT Critical Reasoning Mistakes You Might be Making (Part 2)

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Manhattan Prep GMAT Blog - Tiny GMAT Critical Reasoning Mistakes You Might be Making (Part 2) by Reed Arnold

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As Hemingway did for lions on the Savannah, I have continued my hunt in GMAT Critical Reasoning problems for little mistakes in logic, the tiny tempting answer choices that could trap even the most rational of minds. I have also been consuming as much whiskey as he would have, so plese forgive any typps cos Im perty drnk rite now…

If you missed our first post on the subject, or if you need a brush up, read it here to learn three ways you might slip up on GMAT Critical Reasoning.

Since then, I have found more. As I did last time, I’ll lay out an example that contains the trap, explain the logic behind it, and point you to an actual CR problem that has the same kind of issue. Try to find the right answer to that question and the trap answer that fits the given description.

How Might an Answer Choice Trap You on GMAT Critical Reasoning?

1) It Shifts to or from a Subgroup

Companies have not sold video-game systems that incorporate 3D technology at nearly the levels that they had predicted. Many companies have decided that they should stop investing in hardware that allows 3D gameplay. However, Sow-Knee, a company that makes both televisions and video game systems, is developing a TV screen that has 3D imaging that does not require users to wear glasses, something that has irritated users in the past. Therefore, the head of Sow-Knee’s gaming division has decided to continue developing games for 3D display.

Which of the following would be most useful in evaluating the argument?

A) Do people who play video games like to diversify which brands they buy their home electronics from?

B) Have some people never purchased video game systems because playing video games makes them nauseous and they end up vomiting all over their couches?

You might think that if video games make people projectile vomit then Sow-Knee should stop investing in 3D gaming. However, we were never discussing the whole market of video game systems—we were talking about video game systems that incorporate 3D technology. Similarly, we were never worried about people who can’t play video games at all. Answer choice B has shifted away from that scope. You might think “Oh man, 3D, nausea, this is something we gotta consider!” But those people are already avoiding all video games, and we’re talking about a subgroup of video games and the people who buy video game systems.

This is one of those times where a general explanation is, “That’s out of scope,” but you will want to try to specify why it’s out of scope. In this particular case, the scope was a subgroup. We probably don’t want to switch to another subgroup, and we want to be careful when we move from our subgroup to the group-at-large, because that might take us out of the scope of our argument.

A good indicator that something like this might be going on are words like ‘who,’ ‘that,’ ‘which,’ ‘whose,’ or any other word like this that will specify which ‘type’ of a specific ‘thing’ you’re discussing: nuns who use chainsaws, watches that have rocket launchers—these designate that you’re talking about a specific type of thing.

(EXAMPLE: CR 642 about drinking wine)

2) It Gives Information in a Logically Negated Form

Some homes in the area that have structural issues have been found to be infested with termites. Termites are wood-eating insects that reproduce quickly and can cause load-bearing beams to hollow out, seriously increasing the risk of a collapse. To prevent such collapses from happening, the homeowners association is advising local homeowners to have exterminators visit their house twice a year to spray for termites.

Which of the following, if true, casts the most doubt that the homeowners association’s plan will have the intended effect?

A) Many homeowners will follow the city government’s advisements.

B) Several houses with structural issues—including many that had roof collapses—live in areas where termite infestation rates are very low.

“If the answer’s not B, I’ll eat my foot.”

…How would you like it prepared?

“SON OF A—“

NO, THINK OF THE CHILDREN!

I get it. This one is especially mean (probably meaner than the GMAT). B has just got to weaken the argument, right? The association is saying to spray for termites, and B tells me a lot of the houses that have fallen haven’t even had termites!

But notice that the argument is about collapses that have been caused by termites. The fact that other collapses haven’t been caused by termites is a shift of subgroups talked about above.

“I hate you.”

Well established, and appreciated.

“Okay, but what about A? How does that weaken the argument, if people are going to follow the government’s plan?”

Well, let’s look at A very closely. What is the logical opposite of “Many homeowners will follow the plan”?

Here’s a hint: many homeowners is a far cry from all homeowners.

The logical opposite is: “Some homeowners will not follow the plan.” If some homeowners do not follow the plan, then it makes it less likely that these termite-caused cave-ins will be prevented.

Also realize that in answer choice B, several collapses occurring in low-termite-infested areas means that some other collapses occurred in high-termite-infested areas.

This is very tough. One way to spot this trap is to look out for words like ‘no,’ ‘none,’ ’few,’ ‘some,’ ‘several,’ ‘many,’ ‘most,’ and ‘all.’

In general, consider what negating the answer does to the argument. Sometimes, the negated form of the sentence is obviously correct, so they hide it with this little logical twist.

(And just to drive the point home: the argument is about prevention, not reduction. This is a binary argument).

(EXAMPLE: CR 643, about business loans)  

3) It Strengthens the Argument Instead of Stating an Assumption

Literary critics label certain books ‘guilty pleasures.’ What they mean by this is that a book might not have great literary merit, but is enjoyed because it is low-brow, perhaps even pornographic. However, this is a false distinction and a subtle attempt to diminish the value of these books, which are just as valuable as those that these critics call ‘high literature.’ Writing these ‘guilty pleasures’ takes as much time and talent as writing the pretentious novels these snobbish critics adore so much.

Which of the following is an assumption on which the argument depends?

A) A majority of people say their favorite novel is one that literary critics call a ‘guilty pleasure.’

B) The value of an achievement is derived at least in part from the duration of its creation.

This particular mistake could be generalized as, “It’s the right answer to the wrong problem.” We’ve all been there—it’s a weaken question, but somewhere in working through the twisted logic we forgot that and picked an answer that strengthens. However, this particular version of that error is the one I consider most tempting.

This is an assumption question. We must remind ourselves what a GMAT assumption is and what role it plays. The assumption is an unstated premise to the argument that actually holds the entire argument together. It’s not something that makes the argument better or stronger or more likely; it is something that lets the argument function at all. If the assumption weren’t true, the argument would pretty much be ruined. So a particularly tricky wrong answer choice is an answer that makes my argument better, but that isn’t absolutely necessary to it.

Answer choice A strengthens my conclusion that this ‘cheap literature’ does, in fact, have a lot of value. But my argument could still hold even if every single guilty pleasure novel got lost among the tattering, decaying pages of Twilight and The Firm. I need an assumption that, if false, ruins my argument. Well, if the value of an achievement is not derived from how long it took to make, then my argument falls apart—I was saying these works have value because they take just as long to write. If that’s not where value comes from, then my argument is totally moot, and the fact that people like these novels doesn’t really matter.  

(EXAMPLE: CR 607, about birdlike dinosaurs)

So there you go. Three more tempting answers to keep your eyes out for. I’m quite sure I’ll find more for a part 3. If you think you’ve found something that fits the bill, let us know! Until then, enjoy your foot medium rare with a nice, strong whiskey.

EXPLANATIONS:

CR 642: A and D are both pretty tempting wrong answers, but note that this argument is talking specifically about sulfite allergies and the people who have them. We just don’t care about other substances that might cause an allergic reaction.

CR 643: C is a very, very tempting wrong answer (it’s the one I picked when I first did this problem). It’s actually chosen more often than the right answer, something that is very rare and indicates a real doozy of a question. But if some people choose not to increase their levels of saving, that means some others will increase their levels of savings, so there will be more money saved to loan out to businesses. Also, answer choice D is incorrect for one of the reasons mentioned in this post. Which one do you think it is?

CR 607: Answer choice A not only strengthens the argument—it guarantees it. If there are no descendants of the birdlike dinosaurs, then birds definitely aren’t descendants of the birdlike dinosaurs. But this answer is not something the argument totally depends on. That is, it’s possible that the birdlike dinosaur does have a descendant (a birdlike hippo, for example), but the argument that birds didn’t evolve from birdlike dinosaurs could still hold. 📝


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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