GMAT Math : Absolute Value

Study concepts, example questions & explanations for GMAT Math

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Example Questions

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Example Question #11 : Dsq: Understanding Absolute Value

Of distinct integers , which is the greatest of the three?

Statement 1: 

Statement 2: 

Possible Answers:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

The two statements together are insufficient.

For example, let . Then, from Statement 2, 

Therefore, either  or 

In either case, Statement 2 is shown to be true, since 

and

But if , then  is the greatest of the three. If , then  is the greatest. Therefore,the two statements together are not enough.

Example Question #12 : Dsq: Understanding Absolute Value

Of distinct integers , which is the greatest of the three?

Statement 1: 

Statement 2:  and  are negative.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

Statement 1 alone gives insufficient information.

Case 1: 

, which is true. 

Case 2: 

, which is true. 

But in the first case,  is the greatest of the three. In the second,  is the greatest.

Statement 2 gives insuffcient information, since no information is given about the sign of .

Assume both statements to be true. , and from Statement 1, ; by transitivity, . From Statement 2, . This makes  the greatest of the three.

Example Question #13 : Dsq: Understanding Absolute Value

Let  be any three (not necessarily distinct) integers.

At how many points does the graph of the function 

 

intersect the -axis?

Statement 1:  and  are nonzero integers of opposite sign.

Statement 2:  and  are nonzero integers of opposite sign.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

To determine the point(s), if any, at which the graph of a function  intersects the -axis, set  and solve for .

At this point, we can examine the equation. Since the absolute value of a number must be nonnegative, the sign of  tells us how many solutions exist to this equation. If , there is no solution, and therefore, the graph of  does not intersect the -axis. If , then there is one solution, and, therefore, the graph of  intersects the -axis at exactly one point. If , then there are two solutions, and, therefore, the graph of  intersects the -axis at exactly two points. 

To determine the sign of , we need to whether the signs of both  and are like or unlike, or that . Either statement alone eliminates the possibility that , but neither alone gives the signs of both and . However, if both statements are assumed, then, since  and  have the opposite sign as , they have the same sign. This makes  and , so the graph of  can be determined to not cross the -axis at all.

Example Question #14 : Dsq: Understanding Absolute Value

Which, if either, is the greater number:  or  ?

Statement 1: 

Statement 2: 

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Explanation:

Statement 1 alone gives insufficient information, as is seen in these two cases:. For example, if , then 

However, if , then

Therefore, it is not clear which, if either, of  and  is greater.

Now assume Statement 2 alone.

If  is negative, then , which, being an absolute value of a number, must be nonnegative, is the greater number. If  is positive, then so is , so

.

Therefore, 

.

 is the greater number in either case.

 

Example Question #15 : Dsq: Understanding Absolute Value

Let  be any three (not necessarily distinct) integers.

At how many points does the graph of the function 

intersect the -axis?

Statement 1: 

Statement 2: 

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

To determine the point(s), if any, at which the graph of a function  intersects the -axis, set  and solve for .

At this point, we can examine the equation. For a solution to exist, since the absolute value of a number must be nonnegative, it must hold that . This happens if  and  are of opposite sign, or if . However, Statement 2 tells us that , and neither statement tells us the sign of . The two statements together provide insufficient information.

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