First, fidn the volume of the little cubes that the rectangular prism can hold instide of itself. The formula for volume is length x width x height. This means you have to multiply 1/2 x 1/2 x 1/2. 1/2 x 1/2 x 1/2 = 1/8. Now, since the rectangular prism can hold 840 of these cubes, you need to multiply each cube's volume, 1/8, by 840. 1/8 x 840 = 105.
