Circles

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GRE Quantitative Reasoning › Circles

Questions 1 - 10
1

For , Chelsea can get either a diameter pizza or two diameter pizzas. Which is the better deal?

two

The two values are equal.

Cannot be determined.

Explanation

Therefore the 16 inch pizza is the better deal.

2

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Which of the following is true?

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

The relationship cannot be determined.

Explanation

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Do not be tricked by this question. It is true that can be split into halves, each of which are in length. These halves are not, however, radii to the circle. Since this does not go through the center of the circle, its length is shorter than the diameter. This means that the radius of the circle must be greater than . Now, if it were , the area would be . Since it is larger than , the area must be larger than . Quantity A is larger than quantity B.

3

Circlechord1

O is the center of the circle above.

The circumference of the circle above is .

Quantity A: The length of .

Quantity B:

Which of the following is true?

Quantity B is larger.

Quantity A is larger.

The relationship cannot be determined.

The two quantities are equal.

Explanation

Now, we know that the circumference of a circle is:

or

This means that the diameter of our circle is must be . Given this, we know that the must be shorter than , for the diameter is the longer than any chord that does not pass through the center of the circle. Quantity B is larger than quantity A.

4

Circlechord1

O is the center of the circle above.

The circumference of the circle above is .

Quantity A: The length of .

Quantity B:

Which of the following is true?

Quantity B is larger.

Quantity A is larger.

The relationship cannot be determined.

The two quantities are equal.

Explanation

Now, we know that the circumference of a circle is:

or

This means that the diameter of our circle is must be . Given this, we know that the must be shorter than , for the diameter is the longer than any chord that does not pass through the center of the circle. Quantity B is larger than quantity A.

5

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Which of the following is true?

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

The relationship cannot be determined.

Explanation

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Do not be tricked by this question. It is true that can be split into halves, each of which are in length. These halves are not, however, radii to the circle. Since this does not go through the center of the circle, its length is shorter than the diameter. This means that the radius of the circle must be greater than . Now, if it were , the area would be . Since it is larger than , the area must be larger than . Quantity A is larger than quantity B.

6

For , Chelsea can get either a diameter pizza or two diameter pizzas. Which is the better deal?

two

The two values are equal.

Cannot be determined.

Explanation

Therefore the 16 inch pizza is the better deal.

7

For , Chelsea can get either a diameter pizza or two diameter pizzas. Which is the better deal?

two

The two values are equal.

Cannot be determined.

Explanation

Therefore the 16 inch pizza is the better deal.

8

Circlechord1

O is the center of the circle above.

The circumference of the circle above is .

Quantity A: The length of .

Quantity B:

Which of the following is true?

Quantity B is larger.

Quantity A is larger.

The relationship cannot be determined.

The two quantities are equal.

Explanation

Now, we know that the circumference of a circle is:

or

This means that the diameter of our circle is must be . Given this, we know that the must be shorter than , for the diameter is the longer than any chord that does not pass through the center of the circle. Quantity B is larger than quantity A.

9

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Which of the following is true?

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

The relationship cannot be determined.

Explanation

Circlechord0

O is the center of the circle above.

The length of is .

Quantity A: The area of the circle.

Quantity B:

Do not be tricked by this question. It is true that can be split into halves, each of which are in length. These halves are not, however, radii to the circle. Since this does not go through the center of the circle, its length is shorter than the diameter. This means that the radius of the circle must be greater than . Now, if it were , the area would be . Since it is larger than , the area must be larger than . Quantity A is larger than quantity B.

10

Circle B has a circumference of 36π. What is the area of circle A, which has a radius half the length of the radius of circle B?

324π

81π

18

18π

Explanation

To find the radius of circle B, use the circumference formula (c = πd = 2πr):

2πr = 36π

Divide each side by 2π: r = 18

Now, if circle A has a radius half the length of that of B, A's radius is 18 / 2 = 9.

The area of a circle is πr2. Therefore, for A, it is π*92 = 81π.

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