The base of a rectangular box measures 4 feet by 5 feet. if the volume is 100 cubic feet then the height is

Volume = length x width x height or V = lwh as a formula if you will.

Let's substitute what we know into the formula:

100 = 4 (5) h multiply the 4 (5) on the right side

100 = 20h divide both sides of the equation by 20

5 = h

the height of the rectangular box is 5 feet