The radius of one sphere is twice as great as the radius of a second sphere. Find the ratio of their volumes.

The ratio of the radii is 2:1, so the ratio of their surface areas is 4:1. The area of a sphere is defined by 4 * pi * r^2

So if the radius of the first sphere is 2r, then it would be (2r) ^2 = 4r^2

The rest is the same. So the ratio of their surface areas would be

4 * pi * 4r^2 divided by

4 * pi * r^2

or 4.