Question

What is the radius, in centimeters, of a circle that has a circumference of 16π?

8
16
32
64

Answer 1

8

Explanation:

The circumference of a circle is equal to π , which is a number ≈ 3.14 , multiplied by the diameter of the circle.

Therefore, C = π d .

We know that the circumference, C , is 16 π , so we can say that:

16 π = π d

We can divide both sides by π to see that 16 = d .

We now know that the diameter of the circle is 16 .

We also know that the diameter has twice the length of the radius.

In equation form: 2 r = d

2 r = 16

r = 8

Note that since 2 r = d , the equation C = 2 π r holds and can be used in place of C = π d .

Answer 2

Answer: The radius equals 8cm