GRE Math : GRE Quantitative Reasoning

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : How To Find An Angle In A Hexagon

Quantitative Comparison

Quantity A: The degree measure of any angle in an equilateral triangle

Quantity B: The degree measure of any angle in a regular hexagon

Possible Answers:

The relationship cannot be determined from the information given.

The two quantities are equal.

Quantity A is greater.

Quantity B is greater.

Correct answer:

Quantity B is greater.

Explanation:

We know the three angles in a triangle add up to 180 degrees, and all three angles are 60 degrees in an equilateral triangle. 

A hexagon has six sides, and we can use the formula degrees = (# of sides – 2) * 180. Then degrees = (6 – 2) * 180 = 720 degrees. Each angle is 720/6 = 120 degrees.

Quantity B is greater.

Example Question #1 : How To Find An Angle In A Hexagon

Quantity A: Double the measure of a single interior angle of an equilateral triangle.

Quantity B: The measure of a single interior angle of a hexagon.

Possible Answers:

Quantity A is bigger.

The relationship cannot be determined with the information given.

Quantity B is bigger.

The quantities are equal.

Correct answer:

The quantities are equal.

Explanation:

Begin with Quantity A. We know the measure of one angle in an equilateral triangle is 60. Therefore, double the angle is 120 degrees.

For the hexagon, use the formula for the sum of the interior angles:

where n= number of sides in a regular polygon

If the sum of the interior angles of a regular hexagon is  degrees, then one angle is  degrees.

The two quantities are equal.

Example Question #1241 : Gre Quantitative Reasoning

The perimeter of a regular pentagon is 40 units. What is the area of the pentagon?

Possible Answers:

Correct answer:

Explanation:

The formula for the area of a regular pentagon is given by the equation:

where a is represented by the length of one side. Let's begin by finding the side length of the regular pentagon. If the perimeter is 40, then we can divide by 5 (the number of sides) to find a side length of 8.

If we plug in 8 into the equation:

Example Question #2 : Pentagons

In a five-sided polygon, one angle measures . What are the possible measurements of the other angles?

Possible Answers:

Correct answer:

Explanation:

To find the sum of the interior angles of any polygon, use the formula , where n represents the number of sides of a polygon.

In this case:

The sum of the interior angles will be 540. Go through each answer choice and see which one adds up to 540 (including the original angle given in the problem).

The only one that does is 120, 115, 95, 105 and the original angle of 105.

Example Question #51 : Geometry

In a particular heptagon (a seven-sided polygon) the sum of four equal interior angles, each equal to  degrees, is equivalent to the sum of the remaining three interior angles.

Quantity A: 

Quantity B: 

Possible Answers:

The two quantities are equal.

Quantity B is greater

The relationship cannot be determined.

Quantity A is greater.

Correct answer:

Quantity A is greater.

Explanation:

The sum of interior angles in a heptagon is  degrees. Note that to find the sum of interior angles of any polygon, it is given by the formula:

 degrees, where  is the number of sides of the polygon.

Three interior angles (call them )  are unknown, but we are told that the sum of them is equal to the sum of four other equivalent angles (which we'll designate ):

Further more, all of these angles must sum up to  degrees:

We may not be able to find , or , indvidually, but the problem does not call for that, and we need only use their relation to , as stated in the first equation with them. Utilizing this in the second, we find:

Example Question #3 : How To Find An Angle In A Pentagon

Pentagon2

What is the value of  in the figure above?

Possible Answers:

Correct answer:

Explanation:

Always begin working through problems like this by filling in all available information. We know that we can fill in two of the angles, giving us the following figure:

Pentagon2 2

Now, we know that for any polygon, the total number of degrees in the figure can be calculated by the equation:

, where  is the number of sides.

Thus, for our figure, we have:

Based on this, we know:

Simplifying, we get:

Solving for , we get:

 or 

Example Question #4 : How To Find An Angle In A Pentagon

Pentagon1

Quantity A: The measure of the largest angle in the figure above.

Quantity B: 

Which of the following is true?

Possible Answers:

The relationship cannot be determined.

Quantity B is larger.

The two quantities are equal.

Quantity A is larger.

Correct answer:

Quantity A is larger.

Explanation:

Pentagon1

To begin, recall that the total degrees in any figure can be calculated by:

, where  represents the total number of sides. Thus, we know for our figure that:

Now, based on our figure, we can make the equation:

Simplifying, we get:

 or 

This means that  is . Quantity A is larger.

Example Question #1 : How To Find The Perimeter Of An Acute / Obtuse Isosceles Triangle

What is the perimeter of an isosceles triangle given that the sides 5 units long and half of the base measures to 4 units?

Possible Answers:
18
20
32
14
12
Correct answer: 18
Explanation:

The base of the triangle is 4 + 4 = 8 so the total perimeter is 5 + 5 + 8 = 18.

Example Question #52 : Geometry

An acute Isosceles triangle has two sides with length  and one side length . The length of side   ft. If the length of  half the length of side , what is the perimeter of the triangle? 

Possible Answers:

 foot

 inches

 foot

 inches

 foot

Correct answer:

 inches

Explanation:

This Isosceles triangle has two sides with a length of  foot and one side length that is half of the length of the two equivalent sides. 

To find the missing side, double the value of side 's denominator:

. Thus, half of .

Therefore, this triangle has two sides with lengths of  and one side length of 

To find the perimeter, apply the formula: 





 foot  inches


Example Question #52 : Geometry

An acute Isosceles triangle has two sides with length  and one side length . The length of side  . If the length of  half the length of side , what is the perimeter of the triangle? 

Possible Answers:

Correct answer:

Explanation:

To solve this problem apply the formula: .

However, first calculate the length of the missing side by: .

Thus, the solution is:

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