When it comes to Critical Reasoning questions on the verbal section of the GMAT, the variety that typically adds the most difficulty for examinees is the “Assumption” category. These questions – of which you’ll most certainly see at least a couple on test day – ask you to find an assumption required by the argument provided in the stimulus. For example, question stems might read:

• Which of the following is assumed by the argument above?
• Which of the following is a necessary assumption required by the argument?

Two major themes make the GMAT Critical Reasoning Assumption questions difficult:

1) Assumptions generally don’t jump out at you when you read the argument.

Think about how you’d use the concept of “assumption” in everyday life. You don’t tend to assume things unless they’re just about given. You might assume that the bank is open on a Thursday or that your friend will see the text you sent her. You won’t assume something that’s known to be uncertain: you don’t assume that your forgetful friend filled your gas tank before returning your car, or that there will be an open table at the most popular restaurant in town on a Friday night. When the GMAT asks you for an assumption, it’s probably something that you’re likely to overlook when you read the argument. Therefore you won’t often have a great idea of what the answer will be before you get to the answer choices.

2) Assumptions on the GMAT are often about “addition by subtraction” and not just addition.

Answer choices to assumption questions frequently involve a lot of negation, helping to advance arguments by removing flaws and not by adding new information. Consider the argument:

Bill received the most votes in the school election, so Bill will be the next student council president.

A correct answer to “what assumption is required by that argument” might be something like:

A) Bill was not running for an office other than president.

Note that what this answer does is protect the argument from criticism like “how do we know Bill was running for president?”. A much more satisfying answer would be “the election was for the office of student council president” or something that seemingly adds new value, but Assumption questions very frequently use negation like “was not running” and are therefore longer and more convoluted to read.

Because of all that, an extremely helpful way to approach Assumption questions is to use the Assumption Negation Technique, which essentially says this: take the opposite of the answer choice and then turn the question into a Weaken Question. Taken this way, the answer would read:

A) Bill WAS running for an office other than president.

Which then clearly weakens the conclusion. If he wasn’t running for president, then of course he’s not going to become president. And that should be a much easier answer choice for you to recognize, for a few reasons:

• The Assumption Negation Technique helps to remove the negation that the Testmaker has already implanted to make the question difficult: “was not running” becomes “was running.”
• It’s easier to see small flaws in an argument when you’re in “attack mode” looking to criticize than when you’re looking for subtle ways to improve it.
• Negating answer choices forces you to really think about them in a critical way, which helps you get your head around what are often very dense and convoluted answer choices.

So for example, consider the full-length question:

There are far fewer kidneys available for transplants than there are patients who are waiting for a new kidney. As evidence of this, nearly 85,000 patients are currently on the waiting list for a kidney transplant, but last year only 16,000 kidney transplants took place.

Which of the following is an assumption required by the argument?

A. The number of patients on the kidney waiting list has increased substantially since last year.
B. The number of kidney transplants in the last year is greater than in any previous year.
C. The number of kidney transplants that take place each year is not significantly different from the number of kidneys available over that time period.
D. The process for preparing both donors and patients for a kidney transplant often requires several consultations with a doctor and a cumbersome amount of paperwork.
E. The number of available kidneys has not increased since last year.

On the surface, that argument may seem pretty legitimate; if you can’t find the flaw in the argument at first glance, you’re certainly not alone. But then negate the answers and see how they affect the conclusion. The correct choice, C, would read:.

The number of kidney transplants that take place each year IS significantly different from the number of kidneys available over that time period.

And look how that weakens the conclusion: if the numbers of kidney transplants and available kidneys are known to be significantly different, then the 16,000 transplants isn’t evidence of the number of available kidneys. Negated choice C tells you that you can’t trust the key piece of evidence (16,000 transplants) because that number isn’t anywhere near the larger number of available kidneys. So the argument no longer has a leg to stand on.

Written “forward,” that answer choice is more dense and can be difficult to see as really relevant, but when taken “backward” as the opposite in a Weaken question, it should more-clearly show that you need a close link between the number of kidney transplants and the number of available kidneys to draw that conclusion. And this is why Assumption Negation can be so helpful: assumptions are easy to make. Your mind fills in assumption gaps naturally because those gaps can be so small. In order to awaken your inner critic, it can be helpful to flip the script and turn the challenging Assumption question into a much more manageable Weaken one.