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GMAT Tips – Exponent Errors on the GMAT

Today’s GMAT Tip comes to us from Kaplan. In this article, Kaplan GMAT instructor Bret Ruber explains how to avoid common exponent mistakes when taking the GMAT:

Exponent questions are among those that give GMAT-preppers the most difficulty.  The key to answering exponent questions correctly is to remember all of the rules you must follow.  For example, knowing that a^b x a^c = a^b+c, and a^b x c^b = (ac)^b will be essential to answering exponent questions correctly.

However, you also want to avoid common exponent mistakes.  This is especially important because wrong answer choices in exponent questions, as with the rest of the GMAT, will be based on common test-taker errors.

The most common mistake test-takers make on exponent questions is to erroneously believe that a^b + a^c = a^b+c.  Remember, exponent rules refer to multiplication and division, not addition and subtraction.  When you encounter an exponent question on addition or subtraction, you will usually need to factor out like terms in order to simplify.  For example, if a problem states that 22¹⁰ + 22⁵, rewrite it as (22⁵)(22⁵) + (22⁵)(1).  Then we can factor out 22⁵, which gives us 22⁵(22⁵ + 1).  Be sure to note that you cannot simplify it to 22¹⁵, as this is a completely different number.

By being aware of common exponent mistakes you can ensure that you will not be tempted by wrong answer choices and that you will complete such problem correctly.  This, in turn, will lead to a higher score on test day.

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