Question

What is the surface area of sphere with diameter 23 ft?

Answer 1

A = 4 π r^2
A = 4 π (11.5^2)
A = 4 π (132.25)
And now, how you phrase the answer is up to you and your teacher but I will list three of them:

A = 529π

Pi as 3.14:

A = 1,661.06

Pi in its true form but rounded to the nearest hundredth:

A = 1,661.903

Answer 2

It is: 4*pi*11.5squared = 529*pi square feet