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The basic rule of GMAT Find the Assumption problems on Critical Reasoning is this:
The right answer is the only one that’s necessary to the argument.
But what does that actually mean, and how can you apply it on test day?
Think of an argument as a car. Successfully making an argument is like driving that car to the conclusion. Some parts of a car are truly necessary: the wheels and the engine, for instance. These parts of the car are like assumptions. If you take one away, you can no longer drive that car to where you’re going.
Other parts of the car, like the air conditioning, the radio, the airbags, or even the doors, aren’t necessary. Having them does make your drive more comfortable, faster, or safer. But these parts of the car are like statements that strengthen the argument. They’re nice to have, but when you take them away, you can technically still get to your destination.
When you do GMAT Find the Assumption problems, some wrong answers can be eliminated quickly. Some of them have absolutely nothing to do with the argument. If your argument is like a car, an irrelevant answer is like a xylophone or a platypus. Since a xylophone isn’t part of a car at all, you don’t need to think too hard to eliminate it.
Other ‘easy’ wrong answers are the opposite of what you’re looking for. In our car analogy, an ‘opposite’ wrong answer would be like a flat tire or a traffic jam. They’re not only unnecessary, they’re also harmful.
At this point, you’re probably down to two or three answers, and they all look pretty good. None of them disagree with the argument, and none of them are totally nonsensical.
Try the Negation Test
When you only have a few answer choices left on GMAT Find the Assumption problems, use the Negation Test to spot the right one. To use this test, go one-by-one through the remaining answers. For each one, imagine what would happen if it was false. Here’s an example:
Argument: The state government will pay a percentage of university tuition for high school students who attend a four-year university within the state. This will improve the state’s economy by increasing the number of university-educated adults in the workforce.
Question: Which of the following is an assumption made by the state government in proposing this plan?
A) High school students whose tuition is subsidized will stay within the state after graduating from college.
B) Some students who otherwise would have attended trade schools after high school will instead attend universities within the state.
C) The majority of students who receive the tuition subsidy will successfully graduate from college.
If the first answer choice was false, here’s how it would read:
High school students whose tuition is subsidized will not stay within the state after graduating from college.
This takes the wheels off of the argument. If these students leave the state after graduating, they won’t become part of the state’s workforce. It’s no longer possible for this argument to get to its destination. (A) is an assumption.
If the second answer choice was false, what would happen? This one is a little harder to negate: try it on your own before continuing.
No students who otherwise would have attended trade schools after high school will instead attend universities within the state.
Even if we get rid of the trade school students, it’s still possible that other students—maybe students who otherwise would have gone to out-of-state universities, or students who wouldn’t have gone to college at all—will accept the tuition discount. Taking away this answer choice is like taking away the air conditioning: the argument isn’t quite as good, but it can still reach its destination. That’s why (B) isn’t an assumption.
Let’s try the third one:
The majority of students who receive the tuition subsidy will not successfully graduate from college.
This is a tricky one. It certainly hurts the argument. But is it more like taking the wheels off, or more like removing the radio? The difference is in whether the argument could still get to its conclusion. In this case, it still can, even though it’s harder to get there. Even if the majority of students drop out of college, there could be a significant number of students who don’t drop out. In that case, the conclusion could still be reasonable. (C) isn’t an assumption.
What made (B) and (C) seem reasonable, though? Let’s dive a little deeper.
(B) actually strengthens the argument. If it were true, that would be a point in favor of the state government’s plan. However, an assumption has to do more than just help the argument. It has to be critical to the argument. Strengtheners are tricky wrong answers, because they do relate to the argument, and they do support the conclusion, just like assumptions do. But they break a critical rule of Critical Reasoning: they aren’t necessary.
(C)’s biggest flaw comes from the word majority. If the phrase the majority of were replaced with some, (C) would actually be an assumption. Let’s check it out:
Assumption: Some students who receive the tuition subsidy will successfully graduate from college.
Negation: No students who receive the tuition subsidy will successfully graduate from college.
Suddenly, the engine falls out of the argument! If none of these students graduate, there’ll be nobody to join the workforce. But we didn’t need a majority of them to graduate. We just needed some of them to get there.
The Short Version
When you do GMAT Find the Assumption problems, some of the answer choices will be quick to eliminate: they’ll have nothing to do with the argument, or they’ll go against the author’s reasoning. But once you’ve made those eliminations, the best way to handle the trickier answers is with the Negation Test. Reverse each answer choice in your head, then think about what just happened to the argument. Did the engine fall out of it, or was it more like breaking one of the windows? If there’s any way the argument could still get to its conclusion—even by getting there slowly and awkwardly—you didn’t find an assumption. But if the argument ends up broken down on the side of the road, you know you’ve found the right answer. 📝
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Chelsey Cooley 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 GRE prep offerings here.