GMAT uses data sufficiency questions to test your ability to “reason quantitatively.” This stands in sharp contrast to the problem solving section, which is designed to test how well you manipulate numbers. If you find yourself doing a lot of number crunching on the data sufficiency questions, you are doing something wrong.

  1. Memorize the five answer choices before sitting in the test center; they’re the same for each and every Data Sufficiency question.
  2. Do not rely on a visual assessment of a diagram accompanying a geometry question to determine angle sizes, parallel lines, etc. In addition, do not carry any information over from one question to the next. Each question in the data sufficiency section of the GMAT stands on its own. You can count on seeing at least a few questions where a wrong answer choice tries to capitalize on this common fallacy.
  3. Be careful not to carry over any information from one numbered statement to another. (Making this mistake is remarkably easy, especially under time pressure and in a momentary lapse of concentration.)
  4. If a question asks for a numerical value (as opposed to a quantitative expression that includes variables), the question is answerable only if a numbered statement (1 or 2) yields one and only one possible numerical answer — not a range of values.
  5. If you can eliminate either answer choice (A) or (B), then you can also eliminate answer choice (D).
  6. If either numbered statement (1 or 2) alone suffices to answer the question, then you can eliminate answer choices (C) and (E).
  7. You can use examples to eliminate some choices. For example, you are asked, ‘If x>0 ?’ given 2 conditions. You can find a value for x meeting Condition 1 but not Condition 2. Then find another value meeting Condition 2 but not Condition 1. In this way you can eliminate at least 2 options.
  8. Data Sufficiency questions are designed to test you primarily on quantitative concepts, not on your ability to manipulate numbers (that’s what Problem Solving questions are for). So if you find yourself doing a lot of pencil work, you’re probably on the wrong track.
  9. Just as in Problem Solving questions, in Data Sufficiency questions cast in a real-world setting you should make reasonable real-world assumptions. Don’t split hairs by looking for subtle meanings or ambiguous language. The test-makers are not out to trick you in this way.