Question

A sphere has a diameter of 4ft . what is its surface area ?The surface area of the sphere is _ ft 2(Type an exact answer in terms of pie .)

Answer 1

The formula of the surface area of an sphere is

$SA=4\pi r^2$

where r is the radius

the radius is half of the diameter

r=4/2

r=2 ft

we substitute the values

$SA=4\pi(2)^2=4\cdot\pi\cdot4=16\pi ft^2$

the surface area is 16pi ft^2