GMAT Math: Only a Kitchen Calculator

by on July 16th, 2017

oliver-thomas-klein-144899There are many different approaches in tackling a GMAT Quantitative question effectively. Algebraically, working backwards from the answer choices, considering “lucky twins”—a smart test taker is flexible and takes a fresh new approach by evaluating each quantitative question individually, taking the route that is efficient and effective.

But how does said test taker become the smart test taker—what kinds of signs tip us off that we should go down a certain strategy road for a tricky and/or difficult quantitative question?

Think of the “kitchen calculator”—the kind of cheap plastic, four-digit calculator that you find at a Dollar Store that is only meant for grocery shoppers adding up the bill for bread, cheese, and milk. If you find yourself doing time-consuming multiplication or division calculations, and it seems like something the kitchen calculator cannot handle, stop and reevaluate how you are tackling the question.

Here’s a Data Sufficiency example where the kitchen calculator policy applies:

If a and b are positive integers, is a/b < 9/11 ?

(1) a/b = 0.818

(2) b/a = 1.223

Most test takers immediately take of the route of thinking they need to divide the fraction 9/11—and yikes, is that a messy road (turning out it is 0.818 repeating). Is 9/11 that difficult to divide with a kitchen calculator? No, it is not. But if you immediately recognize something cannot be cleanly divided or multiplied, then you need to think again—the GMAT is not testing your ability to do endless division calculations and make tiny, minute comparisons (say 0.2221 versus 0.2223). Reassess your strategy.

For this particular question, the best way to look at it is to consider rules for inequalities and think of easier numbers to estimate. 9/10 is equal to 0.9, so we know that 9/11 is a little bit under 0.9, so (1) is very likely sufficient on its own.

For statement (2) if I actually think about the initial inequality given—a/b < 9/11, then I should realize that flipping this will give me b/a > 11/9. Obviously, 9/9 is equal to 1, so 11/9 is probably 1.223 making (2) sufficient on its own.

Therefore, our answer is (D).

Some test takers will feel they need to get to some a bit closer and accurate for the sake of their comfortable level and sanity that (D) is the right answer.

If you feel like you are one of these test takers, than an alternative way is knowing common fractional to decimal conversions (1/8, 3/8, 5/8, and so on) including 1/11, which is equal to 0.0909. From there, we are able to simply multiple 9 * 0.0909 to give us 0.81818, helping us with the first statement. 1/9 is equal to 0.1111, so 11 * 0.1111 gives us 1.222, therefore helping us evaluate the second.

But try to consider the kitchen calculator method, or at the very least, understanding the GMAT is not looking for crazy decimal or fractional calculations, and there is probably a reasonably accurate way of estimating the right answer.

Ask a Question or Leave a Reply

The author Veritas Prep gets email notifications for all questions or replies to this post.

Some HTML allowed. Keep your comments above the belt or risk having them deleted. Signup for a Gravatar to have your pictures show up by your comment.