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The Breakdown: GMAT Data Sufficiency

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By QS Contributor Updated Jun 15, 2014
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The Quantative section of the GMAT includes 37 questions grouped into two categories: problem solving and data sufficiency. The latter and more ominous of the two, data sufficiency is designed to measure your ability to:

 

  • Analyze a quantitative problem
  • Recognize relevant information
  • Determine whether there is sufficient information to solve a problem

 

Data Sufficiency Questions Have Two Statements

 

Data sufficiency questions are accompanied by some initial information and two statements, labeled (1) and (2). The two statements lay out possible conditions. You must decide whether the statements given offer enough data to enable you to answer the question.

 

Data Sufficiency questions are not about the actual solution, but deciding whether a solution can be derived in the first place. It is important to analyze each statement independently . In other words, you cannot mix the information from one statement with the other.

 

There are Two Types of Data Suffiency Questions

 

There are two common types of data sufficiency questions:

 

  • Close-ended: Is “Y” divisible by 3?
  • Open-ended: What is the value of “X”?

 

In a close-ended question, you can judge whether each statement is sufficient by determining if its answer is "always Yes" or "always No". A statement is insufficient if its answer is sometimes Yes or sometimes No.

 

In an open-ended question, you can judge whether each statement is sufficient by determining if its answer results in a single value. A statement is insufficient if its answer leads to a range of values, instead of a specific value.

 

There are Five Possible Data Sufficiency Answers

 

The answer choices are always the same; by the time you get to the test and have done enough practice problems, you will not even have to look at the answers if the question is of the data sufficiency variety.

 

  • Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
  • Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
  • BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
  • EACH statement ALONE is sufficient.
  • Statement (1) and (2) TOGETHER are NOT sufficient.

Three Questions You Must Ask

  • Is the information in Statement 1 sufficient to answer the question uniquely, as in, is there only one possible answer? It does not matter what the answer is: yes, no, red, blue. Will it always be the same, no matter what?
  • Is the information in Statement 2 sufficient to answer the question uniquely, meaning do you know that only one answer is possible?
  • If both of these questions are answered with a ”No,” then the third question becomes necessary: Is the information in Statements 1 and 2 together enough to answer the question?

One Data Sufficiency Practice Problem

 

If a real estate agent received a commission of 6 percent of the selling price of a certain house, what was the selling price of the house?

 

(1) The selling price minus the real estate agent’s commission was $84,600.

(2) The selling price was 250 percent of the original purchase price of $36,000.

 

  • Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
  • Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
  • BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
  • EACH statement ALONE is sufficient.
  • Statement (1) and (2) TOGETHER are NOT sufficient.

From (1) we know that $84,600 is 94% (100% - 6%) of the selling price, and thus the selling price, $84,600 / 0.94, can be determined. Therefore (1) alone is sufficient. While from (2) it follows that the selling price is 2.5($36,000). Thus, (2) alone is sufficient. The best answer is the fourth choice.

 

To increase your speed it is important to practice your multiplication and divisibility. Learn the secret rule of 7 at:

https://www.manhattaneliteprep.com/blog/lucky-number-7/

 

About Heather Simon

Heather Simon graduated from Skidmore College, a top liberal-arts institution in Saratoga Springs, with a degree in Studio Art and a minor in English. She works as an academic director at Manhattan Elite Prep, all-the-while pursuing an MFA in Creative Writing and Literary Translation. At MEP, like all of her colleagues, she wears a number of hats and spends her days in front of multiple computer screens. Some of her responsibilities include coordinating test prep courses and tailoring private tutoring packages for individual students; designing course material; and social media and marketing.

 

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