Question

The circumference of a bowling ball is 8pi in. Find the surface area of the bowling ball. Express your answer in terms of pi.

Answer 1

Surface area of a sphere (3D solid's name for ball shaped object) is given by

$SA = 4 \pi r^{2}$

We do not know the radius of the sphere but we can work it out from the circumference $8 \pi$

$Circumference = 2 \pi r$
$8 \pi =2 \pi r$
$r= \frac{8 \pi }{4 \pi }=2$

then
$SA=4 \pi (2)^{2} =16 \pi$