How much water does a 3' cube hold?
Begin with the fact that the volume of one gallon is 231 cubic inches.
Three feet is 36 inches. A 3' cube has 36 * 36 * 36 cubic inches.
36 * 36 * 36 = 46656 cubic inches
Divide the volume of the cube by the volume of one gallon, to
determine how many gallons there are in the cube.
46656 / 231 = 201.97 gallons of water in a 3' cube