Data sufficiency questions ask whether the statements provide enough information to answer a question. You are not expected to calculate a value unless calculation is needed to decide whether an answer is uniquely determined.

1. Standard answer codes

Most data sufficiency questions use these five conclusions:

1. Statement 1 alone is sufficient, but statement 2 alone is not sufficient.
2. Statement 2 alone is sufficient, but statement 1 alone is not sufficient.
3. Both statements together are sufficient, but neither statement alone is sufficient.
4. Each statement alone is sufficient.
5. Even both statements together are not sufficient.

2. What sufficient means

A statement is sufficient only when it gives one definite answer to the exact question. It is not enough for a statement to seem useful or to narrow the possibilities. If two different valid answers remain, the statement is insufficient.

• For a yes-or-no question, the statement must force the same yes or no result every time.
• For a numerical question, the statement must determine one value, not a range.
• For an ordering or relation question, the statement must establish the requested position or relation uniquely.

3. A reliable solving method

1. Read the question first and identify exactly what must be determined.
2. Test statement 1 by itself. Do not use statement 2 yet.
3. Test statement 2 by itself. Do not carry information from statement 1 into it.
4. Only if both are insufficient alone, combine them and test again.
5. Choose the answer code that matches the result.

4. Useful reasoning shortcuts

• Try two cases: if a statement permits two answers that produce different outcomes, it is insufficient.
• Use constraints: inequalities, parity, and directions often decide sufficiency without full calculation.
• Watch for hidden assumptions: do not assume positive numbers, distinct people, or a standard arrangement unless stated.
• Stop once sufficient: additional calculation cannot make a sufficient statement more correct.

Common mistakes

• Combining both statements before checking each one separately.
• Solving for one possible answer and mistaking it for a unique answer.
• Answering a related question rather than the question actually asked.
• Assuming information that is not given, such as an integer being positive.
• Treating a statement as insufficient because it does not reveal every detail, even though it answers the specific question.

Quick revision summary

• Sufficiency means exactly one answer to the question.
• Test statement 1, then statement 2, then both together.
• Two valid outcomes with different answers prove insufficiency.
• Use only the information explicitly provided.