GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #3 : Dsq: Calculating The Length Of The Side Of A Right Triangle

 has right angle  has right angle . Which, if either, is longer,  or ?

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 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.

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient to answer the question.

Correct answer:

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

Explanation:

Assume Statement 1 alone. Since  and  are the right angles of their respective triangles,  and , the segments opposite the right angles, are their hypotenuses, and, subsequently, their longest sides. Specifically, . Since, from Statement 1, , it follows that .

Assume Statement 2 alone. Again,  is the longest side of its triangle, so  . But we cannot determine whether  or  without further information.

Example Question #4 : Dsq: Calculating The Length Of The Side Of A Right Triangle

 is a right triangle. Evaluate .

Statement 1: 

Statement 2: 

Possible Answers:

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.

EITHER statement ALONE is sufficient 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:

Neither statement alone gives enough information to find , as each alone gives only one sidelength.

Assume both statements are true. While neither side is indicated to be a leg or the hypotenuse, the hypotenuse of a right triangle is longer than either leg; therefore, since  and  are of equal length, they are the legs.  is the hypotenuse of an isosceles right triangle with legs of length 10, and by the 45-45-90 Theorem, the length of  is  times that of a leg, or .

Example Question #481 : Data Sufficiency Questions

Given  is a right triangle, which side is the hypotenuse - , or  ?

Statement 1: 

Statement 2: 

Possible Answers:

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.

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.

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:

The side opposite of the right angle is the hypotenuse. Statement 1 alone eliminates  as the right angle, and, as a consequence,  as the hypotenuse - but only .

From Statement 2 alone, we have that , meaning that 

and 

Since  is shorter than , and only , is eliminated as the hypotenuse.

If both statements are assumed to be true, however, then both  and  can be eliminated as the hypotenuse, leaving  as the only choice.

Example Question #4 : Dsq: Calculating The Length Of The Side Of A Right Triangle

 has right angle  has right angle . Which, if either, is longer,  or ?

Statement 1: 

Statement 2: 

Possible Answers:

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.

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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

We are being asked to compare the lengths of the hypotenuses of the two triangles, since  and  are the sides opposite the right angles of their respective triangles.

Statement 1 alone gives insufficient information, as shown by examining these two cases.

Case 1: 

By the Pythagorean Theorem, the hypotenuse  has length

The hypotenuse  has length

Case 2: 

The hypotenuse  has length

and, as in Case 1,  has length .

In both cases,  and , so . But in the first case,  was longer than , and in the second case, the reverse was true.

Statement 2 is insufficient in that it only gives us the congruence of one set of corresponding legs; without further information, it is impossible to determine which hypotenuse is longer.

Now assume both statements are true. Since  and , by the subtraction property of inequality, 

and 

It follows from  and  that  and ; by the addition property of inequality, 

By the Pythagorean Theorem, 

and 

,

so the above inequality becomes, by substitution,

and 

,

proving that  is longer than .

Example Question #9 : Dsq: Calculating The Length Of The Side Of A Right Triangle

Given  is a right triangle, which side is the hypotenuse - , or  ?

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. 

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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

In a right triangle, the angle of greatest measure is the right angle, and the side opposite it is the hypotenuse.

Assume both statements are true. We can eliminate  as the right angle, as it has measure less than both  and . However, we have no information that tells us which of   and  has the greater measure, so we cannot determine which is the right angle. Subsequently, we cannot eliminate either of their opposite sides,  or , respectively, as the hypotenuse.

Example Question #10 : Dsq: Calculating The Length Of The Side Of A Right Triangle

 has right angle  has right angle . Which, if either, is longer,  or ?

Statement 1: 

Statement 2: 

Possible Answers:

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 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.

EITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

The two statements together only give information about the angle measures of the two triangles. Without any information about the relative or absolute lengths of the sides, no comparison can be drawn between their hypotenuses.

Example Question #371 : Geometry

 is a right triangle. Evaluate .

Statement 1:  and 

Statement 2:  is not a 30-60-90 triangle.

Possible Answers:

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.

BOTH statements TOGETHER are insufficient to answer the question.

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

EITHER statement ALONE is sufficient 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.  and , but it is not clear which of the three sides is the hypotenuse of .  is not the longest side, so we know that  or  is the hypotenuse, and the other is the second leg. We explore the two possibilities:

If  is the hypotenuse, then the legs are  and ; since the lengths of the legs are 12 and 24, by the Pythagorean Theorem,  has length

.

If  is a leg, then the hypotenuse, being the longest side, is , and  is the other leg; by the Pythagorean Theorem,  has length

.

Statement 2 alone gives insufficient information in that it only gives information about the angles, not the sides.

Assume both statements are true. If  is the hypotenuse and  is a leg, then, since the hypotenuse measures twice the length of a leg from Statement 1, the triangle is 30-60-90, contradicting Statement 2. Therefore, by elimination,   is the hypotenuse, and, consequently, .

Example Question #12 : Dsq: Calculating The Length Of The Side Of A Right Triangle

Given  is a right triangle, which side is the hypotenuse - , or  ?

Statement 1: 

Statement 2: 

Possible Answers:

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

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.

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.

Correct answer:

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

Explanation:

Since we are comparing angles, we need to identify the angle of greatest measure; in a right triangle, the angle of greatest measure is the right angle, and the side opposite it is the hypotenuse.

Statement 1 is insufficient, since we can eliminate only angle  as the right angle, and, subsequently, only  as the hypotenuse. Similarly, Statement 2 is insufficent, since we can eliminate only angle  as the right angle, and, subsequently, only  as the hypotenuse. But if we are given both statements, we can eliminate  and  as the hypotenuse, leaving  as the hypotenuse.

Example Question #492 : Data Sufficiency Questions

 has right angle  has right angle . Which, if either, is longer,  or ?

Statement 1: 

Statement 2: 

Possible Answers:

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.

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. 

Correct answer:

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

Explanation:

We are being asked to compare the lengths of the hypotenuses of the two triangles, since  and  are the sides opposite the right angles of their respective triangles.

Assume Statement 1 alone. We have that , and , both being right angles, thereby establishing congruence between two pairs of sides and a pair of included angles. By the Side-Angle-Side Theorem, , and, consequently  and  have equal length.

Assume Statement 2 alone. We are only given information about the angle measures, but nothing about the lengths of the sides - actual lengths or comparisons. We can make no conclusions about which hypotenuse is longer.

Example Question #491 : Data Sufficiency Questions

 is a right triangle with right angle . Evaluate .

Statement 1:  has area 24.

Statement 2:  can be circumscribed by a circle with area .

Possible Answers:

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. 

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

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.

Correct answer:

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

Explanation:

Since  is given as the right angle of the triangle , we are being asked to evaluate the length of hypotenuse .

Statement 1 alone gives insufficient information. We note that the area of a right triangle is half the product of the lengths of its legs, and we examine two scenarios:

Case 1: 

The area is 

By the Pythagorean Theorem, hypotenuse  has length

Case 2: 

The area is 

By the Pythagorean Theorem, hypotenuse  has length

Both triangles have area 24 but the hypotenuses have different lengths.

 

Assume Statement 2 alone. A circle that circumscribes a right triangle has the hypotenuse of the triangle as one of its diameters, so the length of the hypotenuse is the diameter - or, twice the radius - of the circle. Since the area of the circumsctibed circle is , its radius can be determined using the area formula:

The diameter - and the length of hypotenuse  - is twice this, or 10.

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