Question

How many cubes needed to fill the rectangular prism

Answer 1

13 good luck on that

Answer 2

To get the answer, you need to find the volume of both the cuboid and the cube.
For the cuboid, the volume is:
V = abh
so 
V = 9 x 4 x 1.5
   = 54 inches^3

For the cube, the volume is a^3,
so
V = 0.5 x 0.5 x 0.5
   = 0.125, which is 1/8
since eight 1/8s can fit into one, the amount that can fit into 54 is
54 x 8, which is 432