GMAT Math Guessing Strategies

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In my many articles on this site about approaching the Computer Adaptive Test, I often recommend that you guess on the most difficult questions. What I haven't shared are any techniques to make you better at guessing.

If you're an experienced standardized-test taker, you probably know some basic guessing strategies:

  • Avoid choices that stand out--for instance, if only one of the five choices has a square root, it's probably wrong.
  • Avoid extreme choices--if one answer is much larger or smaller than the rest, don't choose it.
  • Approximate -- this is particularly useful on geometry problems where you might be able to "eyeball" the size of an angle or the length of a line.

All of these are useful, and can be applied on the GMAT. However, they rarely eliminate more than one choice, so they aren't going to help you rack up very many extra points on the test.

The Big Picture

As with many test-prep strategies, these guessing tips are less effective than they used to be. Remember, the makers of any test pay attention to how students study for the exam, and they adjust accordingly. It's been clear, especially over the last several years, that the GMAC is making it more difficult to guess on GMAT questions.

It's less likely, then, that you'll see a clear oddball answer, or more than one choice that is clearly wrong based on a diagram.

Guessing vs. Guessing Well

The most important guessing strategy is simply to guess at all. It's the best way to ensure that you properly manage your time. You almost certainly won't get every question right, and it's best to save time on some of the ones you don't have the skills to answer.

Any strategic guessing is a bonus. Sure, if you guess on five questions and consistently narrow the possibilities to three choices instead of five, you'll probably guess right twice instead of once. That'll help your score. But it isn't worth spending a lot of extra time trying to "out-think" the test. The test-maker has a lot more time to out-think you when they prepare test items than you do while you're taking the exam.

Other Guessing Strategies

That said, there are some other things to consider. None of these approaches is foolproof--the GMAC knows them too--but they will point you in the right direction.

  • Look for "matched sets." If 6 and -6 are both choices, it's more likely that one of them is correct. On percent and fraction questions, matched sets include those that add up to 1 or 100, such as 1/9 and 8/9, or 65 and 35.
  • Glance at the last step of the question. If you're asked for x - 5, there is probably a wrong answer choice that is 5 away from the correct answer. This is similar to a matched set, only the "set" contains two numbers separated by 5.
  • Advanced tip: If you've spent the time to read the question, even if you don't know how to do it, you may have an idea how others would do it wrong. Consider what sorts of answers would result from the wrong approaches, then avoid those. This can be particularly useful on combinations and permutations problems.

The common theme here is that the wrong answers are chosen for a reason. If 6 is the right answer, -6 is present because there is a step somewhere in the question that leads some test-takers to get a negative instead of positive result. The test-maker isn't choosing wrong answer choices at random.

Finally, any guessing strategy you employ should be based on the content of the question. For instance, don't avoid choice (B) because the correct answers to the last three problems have all been choice (B). There are a few strategies along those lines that may be employed on Data Sufficiency questions, but I'll save those for a future article.



About the author: Jeff Sackmann has written many GMAT preparation books, including the popular Total GMAT Math, Total GMAT Verbal, and GMAT 111. He has also created explanations for problems in The Official Guide, as well as 1,800 practice GMAT math questions.

Total GMAT Math

The comprehensive guide to the GMAT Quant section. It's "far and away the best study material available," including over 300 realistic practice questions and more than 500 exercises!
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