#### Answer

6 inches

#### Work Step by Step

Substitute the given area and solve for r.
$A=\pi r^2$
Substitute the area for A.
$36\pi=\pi r^2$
Divide both sides by $\pi$.
$36\pi \div \pi=\pi r^2\div \pi$
Simplify.
$36=r^2$
Take the square root of each side.
$\sqrt{36}=\sqrt{r^2}$
Simplify.
$6=r$