GMAT Data Sufficiency - Reasoning first, math second

When students come to me for help preparing for the GMAT™ exam, they often possess exceptional math skills, sometimes way more advanced than my own. Their inability to reach a high score on the GMAT Quant Section usually relates to one simple mistake: they are treating the GMAT like a math test, when it is really a “Quantitative Reasoning” test.

In the previous iteration of the GMAT, Data Sufficiency represented almost half of the questions on the Quantitative Reasoning section and was what I called the “The Great Equalizer”— that is, possessing good math skills was not enough to excel if you did not also have strong critical thinking and reasoning skills.

What has changed with the current edition of the GMAT?

With the placement of Data Sufficiency in the Data Insights section, this question type has leaned even more toward assessing critical thinking and reasoning. The pure algebra and arithmetic setups that focused more on math than reasoning are gone. In their place, Data Sufficiency questions are built primarily around statistics, word problems, and data interpretation—topics in which computation alone will never be enough.

GMAC describes the current GMAT™ exam as designed to "hone in on the higher-order critical reasoning and data literacy skills that are especially relevant and applicable in the business environment of tomorrow." Even more than before, Data Sufficiency might be the purest expression of that goal on the entire exam.

What does Data Sufficiency assess as part of the Data Insights section?

Reasoning first, quantitative thinking second. In fact, usually one of the Data Sufficiency questions encountered in the Data Insights section will be entirely devoid of quantitative concepts and be purely verbal in nature (think Critical Reasoning in Data Sufficiency form).

Data Sufficiency can no longer be considered a math problem with some reasoning components. It is a reasoning problem that happens to involve some quantitative thinking—and your performance will reflect exactly how well you handle that distinction.

How does Data Sufficiency go beyond pure math?

Data Sufficiency is an amazingly sophisticated tool for assessing three things:

• Who is highly critical and always questioning given information?
• Who leverages every little piece of information to make the best decision possible?
• Who can recognize the "con" and select a correct answer that differentiates them from other very smart people?

Essentially, Data Sufficiency questions are designed to elicit very particular mistakes related to the skills above. When these mistakes are made, they sometimes relate to an underlying mathematical concept, but more often they are related to particular “cons” that make you under- or over-leverage information. In our curriculum, we present a set of more sophisticated strategies for dealing with these cons, but the important best practices outlined below help you avoid many common mistakes.

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GMAT Data Sufficiency best practices

Understand the rules of the game in Data Sufficiency.

Be clear on what it really means for a statement to be sufficient in a “yes/no” or “what is the value?” question; know the answer choices without thinking; don’t carry information between statements.

Do not go to the statements until you understand the question and organize all the given information.

In difficult GMAT data sufficiency questions, the most important information is almost always hidden in the question stem, not the statements.

Always be critical and always leverage harder.

There are only two mistakes you can make in a GMAT Data Sufficiency question: either you under- or over-leverage the given information. For every statement that you analyze in a data sufficiency question, make sure you are leveraging all available data and be careful that you are not making assumptions. Find the surprisingly sufficient piece of information or the hard-to-recognize contrarian example that makes a statement insufficient.

Make sure your answer is really differentiating you from other smart people.

If something is too good to be true in Data Sufficiency, it usually is. Use the hints within different Data Sufficiency constructs to help prove sufficiency or insufficiency.

Sample GMAT Data Sufficiency question

To show these best practices in action, let’s determine the correct answer to a full official problem. First try this sample question on your own:

The participants in a race consisted of 3 teams with 3 runners on each team. A team was awarded 6 – n points if one of its runners finished in nth place, where 1 ≤ n ≤ 5. If all of the runners finished the race and if there were no ties, was each team awarded at least one point?  

(1) No team was awarded more than a total of 6 points.

(2) No pair of teammates finished in consecutive places among the top five places. 

1. Statement (1) ALONE is sufficient but statement (2) ALONE is not sufficient. 
2. Statement (2) ALONE is sufficient but statement (1) ALONE is not sufficient. 
3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. 
4. EACH statement ALONE is sufficient. 
5. Statements (1) and (2) TOGETHER are not sufficient. 

As is typical in many GMAT Data Sufficiency questions, all of the important information is abstractly presented in the question stem. It is also worth pointing out that this problem has very little to do with math: it is assessing whether you can read carefully and follow every instruction and restriction presented in the problem.

Assessing the question stem

Before moving to the statements, you should summarize all the given information and figure out the exact goal of the question. This starts with determining how many total points are available in this race.

According to the given instructions:

• 5 points go to 1^st place
• 4 points go to 2^nd place
• 3 points go to 3^rd place
• 2 points go to 4^th place
• 1 point goes to 5^th place

This means there are 15 total points that get distributed. The goal is to determine definitively whether each team got at least one point (or not). Make sure to note that all runners finished and there were no ties—if you are told something like this, it usually matters.

Assessing statement (1)

You can see that the upper limit of 6 guarantees that each team must have received at least one point. There is no way to get to a total of 15 without each team contributing some points to the total—that is, 2 teams x 6 points can’t get you to 15.

Since this statement is quite clearly sufficient on its own, you know the answer must be (A) or (D) and you need to then carefully analyze the other statement (when one statement is easy, the other is usually quite tricky!).

Assessing statement (2)

This one takes more time to assess and feels like it might be cleverly sufficient at first glance. However, by considering a few cases that meet this condition, you can prove that the statement is definitively NOT sufficient:

In Data Sufficiency, it is relatively easy to prove insufficiency, but much harder to prove sufficiency. Here you can show definitively that you can get both a yes and a no answer, so you are sure that statement 2 is not sufficient. As a result, the correct answer is (A). 

A few parting thoughts on this question and GMAT Data Sufficiency questions overall:

• Consider carefully why certain restrictions are given. For instance, if it says x is a non-negative integer, I’ll bet you $1000 that zero matters in the question! (Otherwise, they would just say x is positive.)
• If you are not finding some dopamine response with your answer in which you suddenly “get it,” leverage harder or be more critical…you need to find something clever in the problem if it is going to differentiate you at the far end of the curve. For example, if it is easy to solve the problem using both statements, the answer will not be (C)… leverage each statement harder!

When you master all the components of GMAT Data Sufficiency and learn how to play the game cleverly, you can to outperform people with equivalent or even superior math knowledge and increase your Data Insights score dramatically.

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