GMAT Cafe

The Data Sufficiency (DS) question type was created and designed especially for GMAT. This is a very unusual question format and might take sometime to get used with. The test-taker is presented with a question followed by two statements, which may or may not be useful in determining the answer to the question. The test-taker must then determine whether either statement alone is sufficient to answer the question; whether both are needed to answer the question; or whether there is not enough information given to answer the question. As I have mentioned in one of my previous posts, the data sufficiency questions have the same set of answer choices. So, it is a good idea to memorize the answer choices, saves time.

This question type can be best explained with an example. Let us take a very simple example.

But before we proceed, there is a simple tip to remember for data sufficiency questions. The AD/BCE rule.

The rule goes like this: you start the question by checking whether statement 1 alone works. If it does, then either option A or D are correct. If not, then the answer must be either B, C or E.

Question :

If a=2, what is the value of a+b ?

Statements :

1. b=5
2. a+b=7

Answer Choices :

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.

Solution :

Note down the details provided in the question on your scratch paper. Also, note down what the question is asking to determine. So your scratch paper might look something like this :

a = 2

a + b = ??

Now read the statement 1. Note down the details provided in statement 1 on your scratch paper. Now the question we have chosen is extremely simple, so there is actually not much calculation or logic involved. So, on your scratch you will have :

a = 2

a + b = ??

(1) –> b = 5 ( clearly sufficient to answer the question)

Applying the AD/BCE rule, we see that since statement 1 alone is the answer must be either A or D. Lets go to statement 2 to see if it is sufficient.

Note down all the details provided in statement 2 :

(2) –> a + b = 7 ( clearly sufficient to answer the question)

We can see that each statement is ALONE sufficient to answer the question. So we choose D.

Data sufficiency questions are known to be the trickiest of the lot. Some questions may require the test-takers to think on the abstract level. A strong hold on the fundamentals is essential to ace data sufficiency questions, so it is advisable to spend a lot of time practicing these questions.