I am having trouble with this question. I have no idea what to do.

A miniature box used a scale model of a building of a shape of a right rectangular prism. The prism has edge lengths of 2 1/2 inches, 2 1/8 inches, and 1 inch. How many cubes with side lengths of 1/8 inch would be needed to fill the prism?
What is the volume of the prism? Show your work.

2 answers

the prism is 20 cubes by 17 cubes by 8 cubes

cubes = 20 * 17 * 8

vol = 2 1/2 * 2 1/8 * 1 in^3
( 2 1 / 2 ) / ( 1 / 8 ) = 2.5 / 0.125 = 20

( 2 1 / 8 ) / ( 1 / 8 ) = 2.125 / 0.125 = 17

1 / ( 1 / 8 ) = 1 / 0.125 = 8

20 * 17 * 8 = 2720 cubes

OR

Volume of a right rectangular prism:

V = 2 1/2 * 2 1/8 * 1 = 2.5 * 2.125 * 1 = 5.3125 in ^ 3

Volume of a cube:

V = ( 1 / 8 ) ^ 3 = 0.125 ^ 3 = 0.001953125 in ^ 3

5.3125 / 0.001953125 = 2720 cubes