Arectangular prism has a length of 7 cm, a width of 4 cm, and a height of 2 1/2 cm.

the prism is filled with cubes that have edge lengths of 1/2 cm.

how many cubes are needed to fill the rectangular prism?

First solve the volume of the rectangular prism
V = l x w x h
where l is the length
w is the width
h is the height
V = 7 x 4 x 2.5
v = 70 cu cm

then solve the volume of the box
v = e^3
v = 0.5^3
v = 0.125

number of cubes = 70 / 0.125
number of cubes = 560 cubes