GMAT Tip – When to Estimate by a 99th Percentile Scorer

This article outlines a tip on how to tackle questions that require tedious arithmetic on the GMAT.  The key is to know when to estimate.  Here’s a typical arithmetic question on the GMAT:

“At Gigamart, tiles cost $4.25 each, what is the total cost to buy 484 tiles?”

There are two way of answering the above question:

1. Do the arithmetic using the actual numbers
2. Do the arithmetic using approximate numbers

In order to determine which method to use, you should check the answer choices first.  If the answers are very close together, then using actual is likely the best option since using approximate numbers will not help you eliminate enough answers.  For instance, use actual numbers if the answers are:

a) $1987
b) $1998
c) $2011
d) $2028
e) $2057

With these answers, the best way to answer this question is to use the actual numbers.

Your approach should change if the answers are spread apart. For instance, use approximate numbers if the answers are:

a) $113
b) $205
c) $1138
d) $2057
e) $11380

Here you can use the following numbers and equation to solve this problem: $4 x 500 = $2000.  Clearly answer choice D would be correct choice.

So before choosing an approach for tackling questions with tedious arithmetic, check your answers first.  It can save you a lot of time, which is valuable during the GMAT.  Remember keeping up a fast pace is one of the most important GMAT tactics.

You can view a video of this and many other GMAT prep tips at Magoosh.com. Best of luck with the GMAT!