GMAT Math : Problem-Solving Questions

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #701 : Gmat Quantitative Reasoning

Which of the following figures would have exterior angles none of whose degree measures is an integer?

Possible Answers:

A regular polygon with forty-five sides.

A regular polygon with ninety sides.

A regular polygon with thirty sides.

A regular polygon with eighty sides.

A regular polygon with twenty-four sides.

Correct answer:

A regular polygon with eighty sides.

Explanation:

The sum of the degree measures of any polygon is . A regular polygon with  sides has exterior angles of degree measure . For this to be an integer, 360 must be divisible by

We can test each of our choices to see which one fails this test.

Only the eighty-sided regular polygon fails this test, making this the correct choice.

Example Question #1 : Calculating An Angle In A Polygon

Thingy

 

The above diagram shows a regular pentagon and a regular hexagon sharing a side. What is the measure of  ?

Possible Answers:

Correct answer:

Explanation:

The measure of each interior angle of a regular pentagon is 

The measure of each interior angle of a regular hexagon is 

The measure of  is the difference of the two, or .

Example Question #2 : Calculating An Angle In A Polygon

What is the arithmetic mean of the measures of the angles of a nonagon (a nine-sided polygon)?

Possible Answers:

The question cannot be answered without knowing the measures of the individual angles.

Correct answer:

Explanation:

The sum of the measures of the nine angles of any nonagon is calculated as follows:

 

Divide this number by nine to get the arithmetic mean of the measures:

Example Question #5 : Calculating An Angle In A Polygon

You are given a quadrilateral and a pentagon. What is the mean of the measures of the interior angles of the two polygons?

Possible Answers:

Insufficient information is given to answer the question.

Correct answer:

Explanation:

The mean of the measures of the four angles of the quadrilateral and the five angles of of the pentagon is their sum divided by 9.

The sum of the measures of the interior angles of any quadrilateral is . The sum of the measures of the interior angles of any pentagon is .

The sum of the measures of the interior angles of both polygons is therefore . Divide by 9:

Example Question #6 : Calculating An Angle In A Polygon

What is the median of the measures of the angles of a nonagon (a nine-sided polygon)?

Possible Answers:

The question cannot be answered without knowing the measures of the individual angles.

Correct answer:

The question cannot be answered without knowing the measures of the individual angles.

Explanation:

The sum of the measures of the nine angles of any nonagon is calculated as follows:

 

The median of an odd quantity of numbers is the number that falls in the center position when they are arranged in ascending order; for nine numbers, it will be the fifth-highest number. We now need to show that we need to know the actual numbers in order to find the median.

Case 1: Each angle measures .

The set is  and the median is 140.

Case 2: Eight of the angles measure  and one of them measures .

The set is  and the median is 139.

In both cases, the sum of the angle measures is 1,260, but the medians differ between the two.

 

Example Question #701 : Gmat Quantitative Reasoning

Pentagon

Note: Figure NOT drawn to scale.

Given Regular Pentagon . What is  ?

Possible Answers:

Correct answer:

Explanation:

Quadrilateral  is a trapezoid, so  .

, so

Example Question #11 : Calculating An Angle In A Polygon

The angles of a pentagon measure .

Evaluate .

Possible Answers:

This pentagon cannot exist

Correct answer:

Explanation:

The sum of the degree measures of the angles of a (five-sided) pentagon is , so we can set up and solve the equation:

Example Question #702 : Gmat Quantitative Reasoning

The measures of the angles of a pentagon are: 

What is  equal to?

Possible Answers:

Correct answer:

Explanation:

The degree measures of the interior angles of a pentagon total , so

Example Question #12 : Calculating An Angle In A Polygon

What is the measure of an angle in a regular octagon?

Possible Answers:

Correct answer:

Explanation:

On octagon has  sides. The word regular means that all of the angles are equal. Therefore, we can use the general equation for finding the angle measurement of a regular polygon:

, where  is the number of sides of the polygon.

.

Example Question #701 : Problem Solving Questions

What is the measure of one exterior angle of a regular twenty-four sided polygon?

Possible Answers:

Correct answer:

Explanation:

The sum of the measures of the exterior angles of any polygon, one at each vertex, is . Since a regular polygon with twenty-four sides has twenty-four congruent angles, and therefore, congruent exterior angles, just divide:

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