THe weight of a synthetic ball varies directly with the cube of its radius. A ball with a radius of 2 inches weights 0.80 pounds. Find the weight of a ball of the same material with a 3 inch radius.

The cube of the first radius is

2

^{3 }= 8The cube of the second radius is

3

^{3}= 27Set up a propotion to solve for the missing weight

8/27 = .8/x

Cross muliply

8x = 21.6

x = 2.7