# What is the radius of a circle whose circumference is 16π?

Nov 24, 2015

$8$

#### Explanation:

The circumference of a circle is equal to $\pi$, which is a number $\approx 3.14$, multiplied by the diameter of the circle.

Therefore, $C = \pi d$.

We know that the circumference, $C$, is $16 \pi$, so we can say that:

$16 \pi = \pi d$

We can divide both sides by $\pi$ 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: $2 r = d$

$2 r = 16$

color(red)(r=8

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