# If a circle has area 81π square inches, what is the radius?

Jul 31, 2015

r=color(green)(9 inches.

#### Explanation:

The formula for area of a circle is
color(green)(pir^2
Where
$r$ denotes the radius of the circle.

Equating the formula for area with the area of the circle provided.

$\textcolor{g r e e n}{\cancel{\pi} {r}^{2}} = 81 \cancel{\pi}$

${r}^{2} = 81$

$r = \sqrt{81}$

r=color(green)(9 inches.