What Is Assumption on the GMAT?

Definition

An assumption is an unstated premise that an argument relies on. It is a missing piece of logic that must be true for the conclusion to follow from the stated evidence. If an assumption is false, the argument collapses.

Why It Matters on the GMAT

Assumption questions are one of the most common Critical Reasoning types. You'll be asked to identify an assumption, strengthen or weaken an argument (which often involves testing assumptions), or evaluate an argument. Recognizing assumptions helps you quickly parse the logical structure of any argument, improving speed and accuracy across the Verbal section.

Concrete Example

Consider this argument:

“Our company should invest in solar panels because they will lower our electricity costs over the next decade.”

The stated premise is that solar panels lower costs. The conclusion is that we should invest. But the argument assumes that the savings from lower electricity costs will outweigh the initial installation and maintenance expenses. If installation costs are astronomical, the investment might not be worthwhile. That unstated condition is the assumption.

Common Mistakes

• Confusing assumptions with the conclusion or stated premises—assumptions are never explicitly written.
• Choosing an answer that is merely relevant to the topic but not required for the argument to hold.
• Overlooking the difference between an assumption (necessary) and a strengthener (helpful but not required).

How to Practice

Use the Negation Test: take a candidate assumption and negate it. If the argument becomes seriously weakened or falls apart, then it is a necessary assumption. Practice on official GMAT CR questions, and after reading each argument, ask yourself: “What must be true for this conclusion to be valid?” Write down your guess before looking at the answer choices. Over time, you'll spot assumptions faster.