How many 18 inch pieces can you cut from 10 lengths of 8 foot pipe

8 feet x 10 = 80 feet of pipes. 80 x 12 = 960 inches of pipes.

960 inches of pipes / 18 inch piece = 53 and 6/18 = 53 and 1/3

You can get 53 pieces at 18 inches apiece with 6 inches of pipe left over.