The flipside of the “strengthen” question coin on the GMAT is the “weaken” question.  The same set of evidence and conclusion can easily be used for either question type, so it’s always a good idea to start by reading the question itself first, to determine the task before you go to the argument.  After that, your approach is almost identical to the way that you would approach a strengthen question.  Take this question, for example: Healica, a new drug that can cure a common disease that until now has been fatal for 50% of those infected, is made from the root of the New Zealand banananut tree.  The banananut tree is rare in New Zealand, and large quantities of the root are necessary in order to make Healica.  Therefore, if Healica remains in production, the banananut tree will eventually become extinct. If true, which of the following most calls into question the conclusion above?

a) The company that holds the patent to Healica has exclusive rights to produce the drug for another 10 years. b) Healica is expensive, and is not currently covered by most major insurance plans. c) Banananut leaves are considered a gourmet delicacy in many parts of the world. d) The banananut tree, although native to New Zealand, can easily be grown in other parts of the world. e) Producing Healica is time-consuming and expensive for the drug manufacturer.

You should always read the question first, and here the commonly-used phrase “calls into question” means that this question is asking for a weakener. Looking at the argument, we can see from the clue word “therefore” that the conclusion is the last sentence of the argument: “if Healica remains in production, the banananut tree will eventually become extinct.”  Now our job is to find a way to attack the argument, and the easiest way to do that is to identify an existing weakness and exploit it. Here, as in many arguments on the GMAT, the argument has an unstated assumption.  The evidence states that the banananut tree is “rare in New Zealand,” and concludes that extinction will occur because of that.  But for something to be extinct, it must not exist anywhere in the world, and we only have evidence about the tree’s growth in one country.  The unstated assumptions are that the tree doesn’t grow anywhere else, and that growth can’t keep up with the demand for the trees.  A great way to weaken the argument, then, is to attack one of those assumptions. a) The company that holds the patent to Healica has exclusive rights to produce the drug for another 10 years. This choice would require another assumption in order to weaken the conclusion: that the one company producing Healica would not produce enough of it to kill off the banananut tree.  Weakeners, like strengtheners, shouldn’t require so much work to fit into the argument. b) Healica is expensive, and is not currently covered by most major insurance plans. This choice, like choice a), is not closely enough related to the argument. c) Banananut leaves are considered a gourmet delicacy in many parts of the world. This choice makes it more likely that the trees will be in demand and will face extinction.  The argument is strengthened, not weakened, by this choice. d) The banananut tree, although native to New Zealand, can easily be grown in other parts of the world. This is the correct answer, since it exploits the unstated assumptions by explicitly disproving that one of them. e) Producing Healica is time-consuming and expensive for the drug manufacturer. This choice has the same problem as choices a) and b): it takes extra assumptions to fit it into the argument, and that’s not what we want. If you find yourself taking several extra logical steps to explain how an answer choice relates back to the argument and makes the conclusion less likely to follow from the evidence, then the answer choice is probably not close enough to the text of the argument as written.  Remember: stay close to the internal logic of the argument, and don’t bring in specialized outside knowledge!  The test is written so that each question belongs in its own little world, and outside knowledge is rarely relevant to finding the correct answer. A final word on weakeners: remember that the correct answer just has to make the conclusion less likely to follow from the evidence; it doesn’t need to completely disprove the conclusion, although sometimes it will.  So make sure that you’re not looking for unnecessarily extreme answers.

The flipside of the “strengthen” question coin on the GMAT is the “weaken” question.  The same set of evidence and conclusion can easily be used for either question type, so it’s always a good idea to start by reading the question itself first, to determine the task before you go to the argument.  After that, your approach is almost identical to the way that you would approach a strengthen question.  Take this question, for example: Healica, a new drug that can cure a common disease that until now has been fatal for 50% of those infected, is made from the root of the New Zealand banananut tree.  The banananut tree is rare in New Zealand, and large quantities of the root are necessary in order to make Healica.  Therefore, if Healica remains in production, the banananut tree will eventually become extinct. If true, which of the following most calls into question the conclusion above?

a) The company that holds the patent to Healica has exclusive rights to produce the drug for another 10 years. b) Healica is expensive, and is not currently covered by most major insurance plans. c) Banananut leaves are considered a gourmet delicacy in many parts of the world. d) The banananut tree, although native to New Zealand, can easily be grown in other parts of the world. e) Producing Healica is time-consuming and expensive for the drug manufacturer.

You should always read the question first, and here the commonly-used phrase “calls into question” means that this question is asking for a weakener. Looking at the argument, we can see from the clue word “therefore” that the conclusion is the last sentence of the argument: “if Healica remains in production, the banananut tree will eventually become extinct.”  Now our job is to find a way to attack the argument, and the easiest way to do that is to identify an existing weakness and exploit it. Here, as in many arguments on the GMAT, the argument has an unstated assumption.  The evidence states that the banananut tree is “rare in New Zealand,” and concludes that extinction will occur because of that.  But for something to be extinct, it must not exist anywhere in the world, and we only have evidence about the tree’s growth in one country.  The unstated assumptions are that the tree doesn’t grow anywhere else, and that growth can’t keep up with the demand for the trees.  A great way to weaken the argument, then, is to attack one of those assumptions. a) The company that holds the patent to Healica has exclusive rights to produce the drug for another 10 years. This choice would require another assumption in order to weaken the conclusion: that the one company producing Healica would not produce enough of it to kill off the banananut tree.  Weakeners, like strengtheners, shouldn’t require so much work to fit into the argument. b) Healica is expensive, and is not currently covered by most major insurance plans. This choice, like choice a), is not closely enough related to the argument. c) Banananut leaves are considered a gourmet delicacy in many parts of the world. This choice makes it more likely that the trees will be in demand and will face extinction.  The argument is strengthened, not weakened, by this choice. d) The banananut tree, although native to New Zealand, can easily be grown in other parts of the world. This is the correct answer, since it exploits the unstated assumptions by explicitly disproving that one of them. e) Producing Healica is time-consuming and expensive for the drug manufacturer. This choice has the same problem as choices a) and b): it takes extra assumptions to fit it into the argument, and that’s not what we want. If you find yourself taking several extra logical steps to explain how an answer choice relates back to the argument and makes the conclusion less likely to follow from the evidence, then the answer choice is probably not close enough to the text of the argument as written.  Remember: stay close to the internal logic of the argument, and don’t bring in specialized outside knowledge!  The test is written so that each question belongs in its own little world, and outside knowledge is rarely relevant to finding the correct answer. A final word on weakeners: remember that the correct answer just has to make the conclusion less likely to follow from the evidence; it doesn’t need to completely disprove the conclusion, although sometimes it will.  So make sure that you’re not looking for unnecessarily extreme answers.

GMAT critical reasoning questions often ask you to identify the assumption of an argument.  The first step in doing that successfully is understanding what, exactly, they mean by “assumption.”  An assumption in GMAT-speak is the unstated link somewhere in the chain of evidence and conclusion.  Finding the assumption means, basically, finding that gap in the argument and filling it. Assumptions can be roughly divided into “necessary” and “sufficient,” and your approach to tackling an assumption question depends in part on which kind of assumption you’re dealing with.  A necessary assumption MUST be true in order for the conclusion to follow logically based on the evidence presented.  Take, for example, the following simplified version of a GMAT question: Jennie wears glasses.  Jennie also gets A’s in chemistry.  Therefore, Jennie must be smart. Which of the following assumptions is necessary to support the conclusion above? Here, you’re looking at finding the unstated idea that MUST BE TRUE in order for the argument to work logically.  Take a look at the possibilities:

a) Jennie gets good grades in all of her science classes. b) All girls named Jennie are smart. c) Jennie wouldn’t wear glasses if she wasn’t smart. d) Some people who get A’s in chemistry are smart. e) Everyone who gets an A in chemistry is smart.

Now, a few of these choices support the argument’s conclusion.  But only one of them is actually necessary to the argument.  Let’s looks at them one at a time. a) Jennie gets good grades in all of her science classes. This isn’t an assumption of this argument at all.  Jennie’s other science classes are outside the scope of the argument, since they are addressed in neither the evidence nor the conclusion. b) All girls named Jennie are smart. This choice would certainly support the conclusion; if this were true, then the conclusion would HAVE to be true.  But is this statement NECESSARY to the conclusion?  No.  Other girls named Jennie don’t have any necessary significance to this argument.  So this is not a good choice. c) Jennie wouldn’t wear glasses if she wasn’t smart. Again, this choice would be SUFFICIENT to make the argument’s conclusion follow from the evidence.  But is it necessary?  No.  So we’ll bypass this one. d) Some people who get A’s in chemistry are smart. This is the correct choice, because it MUST be true in order for the evidence to follow logically from the conclusion.  What if this wasn’t true, and no one who got an A in chemistry was smart?  If that were the case, then the conclusion would not be true, based on the evidence that Jennie gets A’s in chemistry. e) Everyone who gets an A in chemistry is smart. Once more, this choice is sufficient to support the conclusion, but it’s not necessary.  So it’s not the correct answer to the question that is being posed. Now, hopefully you noticed that the correct answer here is the least extreme relevant statement.  That doesn’t always have to be the case, but for questions that ask for necessary assumptions, it’s a good general guideline.  Be wary of answer choices that are extreme; they will often be sufficient, but not necessary, and will therefore trick test-takers who aren’t careful in evaluating what exactly the question has asked them to find. But what if the question paired with that argument looked more like this? Which of the following assumptions, if true, best supports the conclusion above? Well, in that case, the answer choices would look more like these:

a) Jennie gets good grades in all of her science classes. b) All girls named Jennie are smart. c) Jennie gets A’s in her physics class. d) Some people who get A’s in chemistry are smart. e) Some people who don’t wear glasses are smart.

Just as in the last example, choice a) is not relevant to the argument as an assumption.  But here, choice b) is the correct answer, because if that statement is true, then the conclusion is absolutely true.  Choices c) and e) are irrelevant in the same way that choice a) is, since physics and people who don’t wear glasses aren’t at issue here.  Now, choice d) is NECESSARY to the argument, but it is not the BEST support to the conclusion.  Even if it IS true that some people who get A’s in chemistry are smart, that doesn’t guarantee that Jennie is. Moral of the story: keep a close eye on what the question is asking for, and read accordingly.