Negative reactions to Data Sufficiency questions are both common and understandable. This question type is exclusive to the GMAT, which means that anyone taking the GMAT for the first time will never have seen it before. Unfamiliarity breeds anxiety, which can lead to outright terror on test day. But with a little coaching and a lot of practice, test takers can learn how to attack these problems and turn anxiety into confidence. At first glance, Data Sufficiency questions might not look helpful when trying to assess business school applicants. They don't even require you to calculate answers, so they don't test your math skills. The test makers obviously include these gratuitous questions simply to make people's lives miserable, right? Wrong. Data Sufficiency questions challenge a test taker's thought processes and approach to problem solving. As a leader in the business community, a manager with an MBA must have the ability to analyze a problem, figure out what needs to be done, and delegate the task to the proper employees. The employees will do the work, but the manager needs to assign the proper tasks.
This is the crux of what Data Sufficiency tests. For instance, to determine whether or not the company makes a profit, a manager must total revenue and expenses, and then compare the two values. However, it's up to the accounting department to provide the manager with the totals for revenue and expenses. The manager knows what information is needed, yet others gather it.
HOW DOES DATA SUFFICIENCY WORK?
Does the average of a, b, and c equal c ?
1. c - a = c + b
2. c = 0
- if statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not;
- if statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not;
- if statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient;
- if EITHER statement BY ITSELF is sufficient to answer the question;
- if statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.
HOW DO YOU APPROACH THE QUESTION?
First, look at the question stem. Using the question stem, you have to determine what kind of information you'll need to answer the question. Think of a formula that applies to the problem. In this case, you'd need to use the average formula:
Since in this case the average is the same as one of the terms, you can write:
In order to answer this question, you'd need to know the sum of a and b, and the value of c. Now you can turn to the statements. Kaplan strategy is to start with the simpler one, which in this case is Statement (2).
Here's another Kaplan strategy:
If (2) proves sufficient, you can eliminate (A), (C), and (E). If it is insufficient, you can eliminate (B) and (D). You're told that c = 0. That doesn't help you find the sum of a and b, so (2) is insufficient. Now look at Statement (1). You can rearrange this equation by adding a and subtracting c from each side, leaving you with a + b = 0. This doesn't tell you the value of c, so it is insufficient as well.
Now look at both statements together. If either one of the statements is sufficient by itself, you can skip this step. Since it isn't, you need to combine the statements. You are given the sum of a and b and the value of c, so you can answer the question. It doesn't matter whether the answer is yes or no, but simply that you can answer it consistently. The correct answer to this question, then, is (C).
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