GMAT Data Sufficiency

The five options, every time

1. Statement 1 alone is sufficient, but statement 2 alone is not.
2. Statement 2 alone is sufficient, but statement 1 alone is not.
3. Both together are sufficient, but neither alone is.
4. Each alone is sufficient.
5. Together they are still not sufficient.

A definite no is as sufficient as a definite yes. Sufficiency means the question has one determinate answer — not that the answer is the one you hoped for.

Test in order, and keep them separate

1. Consider statement 1 alone. Sufficient or not?
2. Forget it completely. Consider statement 2 alone.
3. Only if both fail alone, consider them together.
4. Choose from the five.

• Contamination is the classic error: carrying information from statement 1 into your reading of statement 2.
• Solving is the second: working out the value wastes the time the item was designed to save you.
• One case is enough to disprove — find two different answers consistent with a statement and it is insufficient.

Test values that break patterns: zero, one, a fraction between 0 and 1, and a negative. Most insufficient statements are shown insufficient by one of those four.