What is the surface area of a sphere with diameter 18 CM?

Oh, dude, you just need to find the radius first, which is half of the diameter, so that's 9 cm. Then you use the formula for the surface area of a sphere, which is 4πr^2. Plug in 9 for r, square it, multiply by 4, and then multiply by π. That gives you a surface area of 1017π square cm, or about 3190 square cm. Easy peasy!