Surface of a Sphere (C)

A sphere with radius R and center C is the set of all points in the space whose distance from C is R. The surface area of a sphere of radius R is $4\pi R^2$.

Exercises

1.

What is the surface area of a sphere whose radius is 2 feet?

2.

What is the radius of a sphere whose surface area is 12 square feet?

3.

Suppose that radius of a sphere is doubled? What happens to its surface area?

4.

By what proportion should I increase the radius of a sphere to triple its surface area?