# How do you find the radius of a circle when given its circumference?

Dec 6, 2015

If $C$ is a given circumference of a circle and $R$ - its radius, then
$R = \frac{C}{2 \pi}$

#### Explanation:

Circumference of a circle measures as $2 \pi R$, where $R$ is its radius and $\pi$ is a universal constant ($\approx 3.141592635 \ldots$).

Therefore, if circumference $C$ is given, from an equation
$C = 2 \pi R$
we can find $R$:
$R = \frac{C}{2 \pi}$