# If the radius of a circle is 8 inches find the radius of a circle whose area is four times as large?

Nov 7, 2015

16 inches

#### Explanation:

$A = \pi \cdot {r}^{2}$
$\implies A = \pi \cdot {8}^{2}$
$\implies A = 64 \pi$

$A ' = 4 A$

$A ' = \pi \cdot r ' 2$

$\pi \cdot r {'}^{2} = 4 \left(64 \pi\right)$

$\implies r {'}^{2} = 256$

$\implies r ' = 16$