geometry question

Question

You want to put a 5 inch thick layer of topsoil for a new 15 ft by 16 ft garden. The dirt store sells by the cubic yards. How many cubic yards will you need to order? The store only sells in increments of 1/4 cubic yards.

Answer 1

5 in = 5/12 ft

Volume = L * W * h = (5/12)*15*16 = 100 cubic feet

1 cubic yard = 27 cubic feet

100 / 27 = 3.703 cubic yards needed

3.75 cubic yards = 3 and 3/4 cubic yards