The 5 lb. Book: How to Study Logic-Based Reading Comprehension
We’ve very excited because our latest book, the 5 lb. Book of GRE Practice Problems, has just hit the shelves! The book contains more than 1,100 pages of practice problems (and solutions), so you can drill on anything and everything that might be giving you trouble.
Let’s try out one of the problems! Give yourself about 2 minutes to answer this Logic-Based Reading Comprehension (Logic RC). Afterwards, we’ll solve the problem and also discuss how to approach Logic RC questions in general.
Exterminator: Using poisoned food is the most effective tactic for combating a mouse infestation. The mouse will carry the food back to the nest, causing all of the mice to die, while a trap will kill only the one mouse that falls into it. If all signs of the mice disappear for three consecutive weeks after poisoned food is used, the homeowner can be sure that the poison was successful in eradicating the mice.
Which of the following, if true, most seriously calls into question the exterminator’s claim that the absence of signs for three weeks means the mice have been eradicated by the poison?
(A) Because mice hide whenever they sense humans, it is very difficult to see or hear mice even when there is an active infestation.
(B) It is more humane to use live-catch traps that allow homeowners to release the still-living mice outside.
(C) In the spring, many mice that nest in houses begin foraging for food outside and do not return to the comfort of the house until the fall or winter.
(D) There are several different kinds of poison that could be used, some of which are more effective than others.
(E) It sometimes takes longer than three weeks for all of the mice to ingest and die from the poison.© ManhattanPrep, 2013
There are several important steps that help us to answer Logic-Based Reading Comprehension questions both effectively and efficiently.
First, just note that these passages tend to read like short arguments—someone’s trying to conclude something, or two people / groups are disagreeing about something, and so on.
(1) Identify the Question Type
Start with the question stem, not the passage itself. Why? The question stem gives you an idea of the type of logic you’re going to need to employ when reading the argument. In addition, sometimes the question stem will give us the argument’s conclusion.
The question might ask us to strengthen or weaken the conclusion, find an assumption, draw an inference, resolve a paradox, or analyze the structure of the argument.
In this case, the question asks us which answer choice most seriously calls into question the claim made in the argument—in other words, this is a Weaken the Conclusion question.
(2) Deconstruct the Argument
These arguments contain several different kinds of information:
Premises: Facts or opinions that support some claim or conclusion. All arguments contain premises.
Conclusion: A claim that the author of the argument or someone in the argument is trying to make. Most arguments contain conclusions, but not all.
Assumptions: Pieces of information that are NOT explicitly stated in the argument. The person making the claim must believe the assumptions to be true in order to draw that conclusion—but he does not actually state these assumptions in writing.
Counter-premises: Facts or opinions that go against the claim the argument is trying to make.
When reading the argument, we want to identify what roles the different pieces of information play and how they fit together. It’s a good idea to jot down some notes to help you figure this out.
Here’s one possible set of notes (though notes will vary greatly from person to person):
E: poison food = best to kill M
M PF Ã nest, kill all
trap = only 1
3 wks no sign à PF killed all M
Note that there are a couple of different things here that we could label the conclusion. The first sentence contains a claim that poisoned food is the best way to get rid of mice. The final sentence claims that, if all signs disappear for 3 weeks, then the poisoned food achieved the goal to eradicate the mice. Which is the conclusion?
In this case, it’s especially helpful to read the question stem first, because the question itself contains the conclusion they want us to use: the claim that 3 weeks of no signs = success for the poisoned food.
Finally, put it all together: we’re looking for something to weaken the claim that, if there are no signs of mice for 3 weeks, then the poisoned food successfully killed them all.
(3) Eliminate Answers
Examine each answer choice in turn. At first, focus on eliminating answers that you’re confident are wrong. Then compare any remaining (tricky!) answers.
(A) Because mice hide whenever they sense humans, it is very difficult to see or hear mice even when there is an active infestation.
This answer is extraordinarily tempting—but it’s wrong! This choice only says that it’s hard to see or hear the mice, but the conclusion says that all signs of the mice must disappear. There are other possible signs besides physically seeing or hearing the mice themselves. You might find food crumbs scattered around in the morning after they raided your kitchen all night, or a torn-open sack of bread. You might find droppings, to put it delicately. ? There’s a mismatch between the very broad claim (all signs) made and what is covered in this answer choice. Eliminate A.
(B) It is more humane to use live-catch traps that allow homeowners to release the still-living mice outside.
I’m sure many people believe this to be true (in fact, it’s hard to argue that it’s more humane to kill the mice!), but this choice doesn’t address the specific claim we were asked to attack: that no signs for 3 weeks = mice are dead from poison. Eliminate B.
(C) In the spring, many mice that nest in houses begin foraging for food outside and do not return to the comfort of the house until the fall or winter.
Hmm. This is interesting. Let’s say that I happen to carry out the exterminator’s plan just at the start of spring. I put all of the poisoned food out and, hooray, I don’t see any signs of mice for 3 solid weeks! But maybe the mice aren’t dead. Maybe they’re just all outside, living off of the abundance of fresh greens, and come September or October, I’m going to start seeing signs of them in the house again.
This answer choice provides an alternate reason for the disappearance of the mouse-in-the-house signs. They aren’t dead—they’ve just gone someplace else. (In which case, oh no, they might be back in a few months!) Leave this one in.
(D) There are several different kinds of poison that could be used, some of which are more effective than others.
I have no doubt that this is true in the real world. Like answer B, however, this choice does not address the specific claim that we were asked to weaken. Note that both answers B and D are true in the real world but don’t actually answer the question. Be very careful with these—never pick an answer because you think it sounds good according to your real-world ears. It has to address the question that was asked. Eliminate D.
(E) It sometimes takes longer than three weeks for all of the mice to ingest and die from the poison.
Another extra-tricky answer! When I first read this one, I thought—oh, maybe it’ll take longer than 3 weeks to kill all the mice! So maybe the conclusion is wrong to state 3 weeks as the timeframe. And, yes, maybe it will take longer than 3 weeks. In fact, let’s say it does—and let’s say that, after 1 week, we notice signs of the still-living mice. Well, that just means that the poison hasn’t yet successfully gotten rid of the mice. Maybe the signs will disappear during weeks 2, 3, and 4. The exterminator never says anything about when the three consecutive weeks must occur relative to when the poisoned food is distributed. Eliminate E.
The correct answer is C.
Key Takeaways for Logic-Based Reading Comprehension Problems
(1) Know your three steps: 1 identify the question; 2 deconstruct the argument; 3 eliminate answers.
(2) One common (and very tempting!) trap is an answer that addresses issues or concepts related to the conclusion but falls short of impacting the specific conclusion given. We saw this type in answers A and E.
(3) Real-world answers can also be tempting. As the test goes on, we get more mentally fatigued and we sometimes forget to draw the all-important boundary line between what the argument actually says and what we know or might infer in the real world. Don’t let up! Hold closely to the actual text of the passage. ?
© Manhattan Prep, 2013
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Stacey Koprince is a Manhattan Prep instructor based in Montreal, Canada and Los Angeles, California. Stacey has been teaching the GMAT, GRE, and LSAT for more than 15 years and is one of the most well-known instructors in the industry. Stacey loves to teach and is absolutely fascinated by standardized tests. Check out Stacey’s upcoming GRE courses here.