GMAT Math : Geometry

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #2 : Dsq: Calculating The Height Of A Right Triangle

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What is the length of the height  of right triangle , where   is a right angle?

(1) 

(2) 

Possible Answers:

Statements (1) and (2) together are not sufficient.

Each statement alone is sufficient

Statement (1) alone is sufficient

Statement (2) alone is sufficient

Both statements together are sufficient

Correct answer:

Both statements together are sufficient

Explanation:

Since we are told that triangle ABC is a right triangle, to find the height, we just need the length of at least 2 other sides. From there, we can find the length of the height since in a right triangle, the height divides the triangle into two triangles with the same proportions. In other words . Therefore, we need to know the length of the sides of the triangle.

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

Consider right .

I) The longest side, , has a length of  meters.

II) .

What is the height of ?

Possible Answers:

Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.

Both statements are needed to answer the question.

Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.

Neither statement is sufficient to answer the question. More information is needed.

Either statement is sufficient to answer the question.

Correct answer:

Both statements are needed to answer the question.

Explanation:

The height of a right triangle will be one of its side lengths.

I) tells us the length of our hypotenuse.

II) gives us the other two angle measurements.

They are both 45 degrees, which makes JKL a 45/45/90 triangle with side length ratios of  .

Which we can use to find the height.

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

What is the height of the right triangle?

  1. The area of the right triangle is .
  2. The base of the right triangle measures .
Possible Answers:

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Each statement alone is sufficient to answer the question.

Correct answer:

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Explanation:

Statement 1: 

More information is required to answer the question because our base and height can be  and  or  and  

 

Statement 2: We're given the base so we can narrow down the information from Statement 1 to  and . If the base is , then the height must be 

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Example Question #5 : Dsq: Calculating The Height Of A Right Triangle

What is the height of the rigth triangle?

  1. The area of the right triangle is .
  2. The perimeter of the right triangle is 
Possible Answers:

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Each statement alone is sufficient to answer the question.

Statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Correct answer:

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Explanation:

Statement 1: 

Additional information is required because our base and height can be  and  and , or  and 

Statement 2: 

Even if we solve for our two values, we will not be able to determine which is the base and which is the height.

 

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

 

Example Question #161 : Triangles

Which interior angle of  has the greatest measure?

Statement 1: 

Statement 2:  is a right angle.

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.

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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

If Statement 1 is assumed, then by the converse of the Pythagorean Theorem, the triangle is a right triangle with right angle , which is explicitly stated in Statement 2. If  is a right angle, then the other two angles are acute, since a triangle must have at least two acute angles. A right angle measures  and an acute angle measures less, so from either statement, we can deduce that  is the angle with greatest measure.

Example Question #411 : Geometry

 

  Triangle

Note: Figure NOT drawn to scale.

 are acute.  Is  a right angle?

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

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

A right triangle must have its two acute angles complementary; if Statement 1 is assumed, then this is false, the triangle is not a right triangle, and  is not a right angle.

If Statement 2 is assumed, then we apply the converse of the Pythagorean Theorem to show that the triangle is not right. The sides of a triangle have the relationship 

 

only in a right triangle. If , then the statement to be tested would be 

This statement is false, so the triangle is not a right triangle, and  is not a right angle. 

Example Question #172 : Triangles

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 is a right triangle , where  is a right angle, and  is a height of the triangle. What is the measurement of  

(1) 

(2) 

Possible Answers:

Both statements taken together are sufficient

Each statement alone is sufficient

Statement 2 alone is sufficient

Statements 1 and 2 taken together are insufficient

Statement 1 alone is sufficient

Correct answer:

Each statement alone is sufficient

Explanation:

Since we are already told that triangle ABC is a right triangle, we just need to find information about other angles or other sides.

Statement 1 allows us to calculate , simply by using the sum of the angles of a triangle, since we know AEC is also a right triangle because AE is the height.

Statement 2 is also sufficient because it allows us to know angle . Indeed, in a right triangle, the height divides the triangles in two triangles with similar properties. Therefore angle  is the same as .

 

Therefore, each statement alone is sufficient.

Example Question #3 : Dsq: Calculating An Angle In A Right Triangle

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Given:  is a right triangle with height  and   is a right angle.

What is the size of  

(1) 

(2) 

Possible Answers:

Statement 1 alone is sufficient

Statements 1 and 2 taken together are not sufficient

Both statements together are sufficient

Statement 2 alone is sufficient

Each statement alone is sufficient

Correct answer:

Statement 1 alone is sufficient

Explanation:

In order to find the angles of right triangle ABC, we would need to find the length of the sides and maybe found that the triangle is isoceles, or is a special triangle with angles 30-60-90. 

Statement one tells us that the height is equal to half the hypothenuse of the triangle. From that we can see that the triangle is isoceles. Indeed, an isoceles right triangle will always have its height equal to half the length of the hypothenuse. Therefore we will know that both angles are 45 degrees. Statement 1 alone is sufficient.

Statement 2 alone is insufficient because we don't know anything about the other sides of the triangle. Therefore it doesn't help us.

 

Example Question #4 : Dsq: Calculating An Angle In A Right Triangle

You are given two right triangles:  with right angle , and  with right angle 

True or false: 

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.

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.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

For , it is necessary that corresponding angles be congruent - specifically,  and . We show that the statements together are insufficient by assuming them both to be true and examining two cases:

Case 1: .

Case 2:   and .

Both cases fit the main body of the problem and both statements, but in the first case, , and in the second case, . The statement  holds only in the first case but not in the second. (Note that in both cases, , but this is a different statement.)

Example Question #6 : Dsq: Calculating An Angle In A Right Triangle

Given a right triangle   with right angle , what is the measure of ?

Statement 1: 

Statement 2: 

Possible Answers:

EITHER STATEMENT ALONE provides sufficient information to answer the question.

STATEMENT 1 ALONE provides sufficient information to answer the question, but STATEMENT 2 ALONE does NOT provide sufficient information to answer the question.

BOTH STATEMENTS TOGETHER provide sufficient information to answer the question, but NEITHER STATEMENT ALONE provides sufficient information to answer the question.

STATEMENT 2 ALONE provides sufficient information to answer the question, but STATEMENT 1 ALONE does NOT provide sufficient information to answer the question.

BOTH STATEMENTS TOGETHER do NOT provide sufficient information to answer the question.

Correct answer:

EITHER STATEMENT ALONE provides sufficient information to answer the question.

Explanation:

Corresponding angles of similar triangles - including the same triangle, considered in different configurations - are congruent. It follows from Statement 1 alone that . The measures of the acute angles of a right triangle add up to , so:

 

Assume Statement 2 alone. By the 45-45-90 Theorem, since the legs of the right triangle are of equal length, the acute angles of the triangle, one of which is , measures .

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