# What is the radius of a circle with a circumference of 22?

Nov 10, 2015

Approximately $\frac{7}{2}$, exactly $\frac{11}{\pi}$

#### Explanation:

The circumference of a circle is of length $2 \pi r$ where $r$ is the radius.

So in our case

$22 = 2 \pi r$

Divide both sides by $2 \pi$ to get:

$r = \frac{22}{2 \pi} = \frac{11}{\pi}$

One well know approximation for $\pi$ is $\frac{22}{7}$, which gives the approximation:

$r \approx \frac{11}{\frac{22}{7}} = \frac{7}{2}$