# What is the radius of a 40 inch circle?

Sep 25, 2015

Approximately 6.37 inches

#### Explanation:

The circumference of a circle is $2 \pi \cdot r$

Therefore for a circle of circumference 40 inches and radius r inches

$2 \pi \cdot r$ = 40

r = $\frac{40}{2 \pi}$

r = $\frac{20}{\pi}$

$\pi$ = approx. 3.14159

Therefore r = approx. $\frac{20}{3.14159}$ = 6.37 inches