A cubical block of metal weighs 6 pounds. How much will another cube of the same metal weigh if its sides are twice as long?
Let us say that each side of the original block has length 'x'; then its volume is x³.
If you make each side twice as long, each side will have length '2x'; then its volume is (2x)³ = 8x³.
So, the new cube will have 8 times the volume of the old cube.
If the old cube weighs 6 pounds, the new cube will weigh 6 x 8 = 48 pounds.