Question

A right cubic prism has edges of 2 1/2 inches. How

many cubes with side lengths of inches would
be needed to fill the prism?
A. 125 cubes
B. 37.5 cubes
C. 18.75 cubes
D. 15.625 cubes

Answer 1

Option D, the volume is 15.625 cubes

Explanation:

For a cube of side length L, the volume is:

V = L^3

for the smaller cubes, we know that each one has a side length of 1 in, then the volume of each small cube is:

v = (1in)^3 = 1 in^3

Then:

1 in^3 is equivalent to one small cube

Here we know that the side length of our cube is (2 + 1/2) in

Then the volume of this cube will be:

V = [ (2 + 1/2) in]^3

To simplify the calculation, we can write:

2 + 1/2 = 4/2 + 1/2 = 5/2

Then:

V = ( 5/2 in)^3 = (5^3)/(2^3) in^3 = 125/8 in^3 = 15.626 in^3

This means that 15.625 small cubes will fill the prism.

So the correct option is D.