GMAT Data Sufficiency: Process of Solving

In the GMAT (Quant) Math section, a student will come across two types of questions:

  1. Problem Solving (PS) Questions, and
  2. Data Sufficiency (DS) Questions

Now, most students are familiar with problem solving (PS) type of questions because they are the typical multiple-choice questions (MCQs) where a question stem is given along with 5 options (as shown below):

Question : If x is a positive integer and x2 + 5x – 14 = 0, what is the value of x?

Answer Choices:

A. -7

B. -2

C. 2

D. 7

E. None of the above

However, for most students Data Sufficiency questions are a completely new type and a lot of these students struggle in understanding the right way to solve them.

Keeping the challenge that students face in mind, we have decided to come up with a 4-part article, in which we’ll cover the following aspects of Data Sufficiency:

  1. Data Sufficiency: Process of Solving
  2. 5 Practice Questions on DS: Understand when the answer is Option A, B, C, D, or E.
  3. 2 type of DS questions and 2 common mistakes made by students
  4. Common DS Traps set by GMAT.

Once you go through these 4 articles, you will have a clear understanding of how to approach a DS question and solve it methodically without falling for any traps.

So, what are we waiting for? Let’s get started!

Introduction to DS

In a DS question, you will find a question stem and two statements – statement 1 and statement 2. (as shown below) –

Question : If x is a positive integer, what is the value of x?

(1) x2 = 9

(2) 4x + 3y = 15  

Along with that, there will be five option choices which are standard in DS questions. GMAT never changes the order of these options, so it is best to remember them once and for all –

A. Statement (1) alone is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) alone is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statement (1) and (2) TOGETHER are NOT sufficient.

The task for a student is to read the question stem carefully, jot down relevant information given in the stem, and understand what they need to find out. Next, they need to use the information given in the statements and decide whether they can answer the question using the given statements or not.

Now, this may either seem a bit too confusing or a bit too obvious. So, let’s go through the steps involved in solving the question :

How to solve Data Sufficiency questions following the right steps?

Steps Involved

As mentioned above, first read the question stem and see if there is any relevant information that may help you to solve the question.

Note that the question stem does not have all the information needed to solve the question. It just provides some pieces of information that may help you get to the final answer.

For example, in the above sample question, the question stem is really simple – ‘If x is a positive integer, what is the value of x?’

So, what information can we gather from the above statement?

We can infer that x is a positive integer. Which means x can be 1, 2, 3, 4…and so on. This is an important information and we should always jot down all relevant information at one place.

Now, we’ll look at what we need to find, which in this case is the value of x. Once, we have understood what we need to find out, we should move ahead and read the first statement.

While reading the first statement, we should focus on only the first statement and not read the second statement simultaneously. If you are wondering why, look at the first option given to us –

A. Statement (1) alone is sufficient, but statement (2) alone is not sufficient.

This means, our first step is to just look at S1 and try to figure out if we can find the answer without the help of S2.

Now, while analyzing Statement 1, we can come across two scenarios –

Statement 1 is sufficient:

The first scenario is when Statement 1 is sufficient to answer the question. So, if the statement 1 is sufficient, should we mark the answer as Option A?

Well, no, don’t do that. If you observe all the options carefully, you’ll notice that Option D says:

D. EACH statement ALONE is sufficient. So, if statement 1 alone is sufficient, we should not jump to the conclusion that the answer is A.

We should infer that the answer could be either A or D. And to figure out which one can be the answer, we’ll analyze statement 2.

While reading the statement 2, let’s forget all about statement 1. Our task is to try and get the answer from Statement 2 alone –

So, while analyzing S2, there can again be two possibilities –

S2 alone is also sufficient:

After analyzing the statement 2, we realize that even statement 2 is sufficient to answer the question independently!

If that’s the case, then we’ll end up marking the answer as Option D.

D. EACH statement ALONE is sufficient.

S2 alone is not sufficient:

However, it is quite possible that statement 2 alone is not sufficient to answer the question.

If that’s the case, then we’ll end up marking the answer as Option A, since statement 1 alone was sufficient to answer the question.

Statement 1 alone is not sufficient:

Now, we’ll look at a scenario where Statement 1 is not sufficient.

If statement 1 alone is not sufficient to answer the question, then we can be sure that the answer cannot be A or D. So, we’ll eliminate those option choices and move on to analyse statement 2 individually and once again we’ll come across 2 scenarios –

S2 alone is also sufficient:

After analyzing the statement, we realize that statement 2 is sufficient to answer the question independently!

If that’s the case, then we’ll end up marking the answer as Option B.

B. Statement (2) alone is sufficient, but statement (2) alone is not sufficient.

S2 alone is not sufficient:

However, it is quite possible that statement 2 alone is also not sufficient to answer the question.

If that’s the case, then we’ll try and combine both the statements and see if we can get the answer by using both information given in the two statements.

Combining both statements:

Case 1:

On combining both the statements, if we can find the answer, then we’ll mark the answer as Option C.

Case 2:

On combining both the statements, if we cannot find the answer, then we’ll mark the answer as Option E.

GMATWhiz 3-Step Process

At GMATWhiz, we believe in simplifying the process. Hence, we came up with a 3-step process that encapsulates all the above cases easily –

Step 1: Analyse Question Stem

In this step, we jot down all the relevant information and figure out what we need to find out.

Step 2: Analyse Statements Independently (And eliminate options) – AD/BCE

Statement 1:

We analyze the first statement individually.

Statement 2:

We analyze the second statement individually.

Step 3: Analyse Statements by Combining

If we don’t get the answer from either of the statements alone, then we combine both and see if we can get the answer together.

Keep in mind that we combine only when we cannot get the answer from both the statement individually! Do not make the mistake of combining them in the initial stage, just because it seems that you may get the answer!

Also, remember that the third step is optional and may not be required if we get the answer from either S1 or S2 or both of them individually!

Conclusion

We hope this article helped you understand the flow in which you need to approach a DS question. However, just knowing the work-flow is not enough to be master the DS questions. You need to learn to apply it in different scenarios to get a full understanding of it.

In the next article, we’ll take up 5 different questions and I’ll show you how we can apply our 3-step process which inculcates the DS flowchart to solve any DS question. These 5 questions will help you understand in which scenarios we get the answer as Option A, B, C, D, or E. So, do make sure to go through it to solidify your understanding.