Geno has a fish tank that is a rectangular prism with a base measuring 7 feet by 3 feet and a height of 3 feet. he wants to fill the base of the tank with pebbles 6 inches high. how much space, in cubic feet, do the rocks in the tank cover?

Well, first we would have to convert feet into inches. 7ft*3ft*3ft=84in*36in*36in. Since he wants to fill the bottom with pebbles 6 inches high, that would subtract 6 inches from the height of 36 inches. So the volume of the pebbles is 84*36*6 which equals 18144 inches cubed. The answer has to be in cubic feet, however, so 18144/1728=10.5 feet cubed. You get the 1728 from 12*12*12, because you have to divide the number of inches in a foot and cube that number and then divide the number of inches cubed (18144) by 12^3, so the answer is 10.5ft.^3! Hope this helps!