Do Your Work Early on Data Sufficiency

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This tip for improving your GMAT score was provided by David Newland at Veritas Prep.

Most people seem to want to jump right to the statements on Data Sufficiency questions. Since the correct answer is based on the statements being “sufficient” or “not sufficient,” students usually put their whole focus on the statements.

However, high-scoring test takers know that the question stem—and even the question itself—can be an integral part of the process. If you do some work before you go to the statements, you can become much more efficient at Data Sufficiency.

Rephrase the question.
A simple way to do your work early is to rephrase the question. Take a simple question such as: “Is the triangle equilateral?” You know that an equilateral triangle has all sides and angles equal. You could rephrase the question as: “Does the triangle have three 60 degree angles?”

It may seem a waste of time to do this, but I have found, in teaching the question to hundreds of students, that if I prompt them to rephrase the question to ask, “Does the triangle have three 60 degree angles?” that about 50 percent more students in class get the correct answer. This is because on the GMAT it is not enough to know something. You have to use that information in the right way at the right time.

Here is a further example of a question stem, and this one is paired with the answer choices:

“If x is an integer, is x/2 an even integer?
1)      x is a multiple of 2
2)      x is a multiple of 4

There are several ways to approach this question, but rephrasing the question stem is probably the best. What does it take for x to be divided by 2 and still be an even integer? It would take a multiple of 4 right? You need to have at least 2-squared in order to divide by 2 and still have an even number.

So rephrase the question as “Is x a multiple of 4?” You can see that at this point that the question is already answered. Statement 2 is sufficient while statement 1 is not. The correct answer is B.

Focus on the Formula.
Another way you can do your work early on DS is to focus on the formula. On questions that require a formula—such as geometry, venn diagram, work/rate, and percentage increase—write out the formula and decide which numbers are necessary. Then you can simply check to see if the statements provide these numbers.

A simple example of this technique can be shown using a question for the Veritas Prep Foundations of Logic book.

“By what percent was the price of a certain candy bar increased?
(1)    The price of the candy bar was increased by 5¢.
(2)    The price of the candy bar after the increase was 45¢.”

This question asks for a percentage increase. The formula for percentage increase is (New Value-Original Value)/Original Value, or state an alternate way: Increase/Original Value.

Which clues would help you to find the percentage increase? 1) New Value 2) Original Value 3) Increase. As you can see from the formulas, you only need any two of these three clues in order to be able to use the formula.

Statement 1 gives you one of the clues (increase), and statement 2 gives you the other clue (new value). You need both clues in order to use the formula, so the correct answer is C.

This is a simple example, but the technique becomes even more useful with complex questions that are likely to generate confusion. Focusing on the formula is a way to make sense of the problem before you get caught up in the statements. “Rephrasing the question” and “focusing on the formula” are two ways that you can do your work early on Data Sufficiency.

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