Formula for Volume of Rectangular Prism: V = L * W * H, or V = B * H.
V = Volume
B = Area of Base
H = Height from Base
Your answer would be, 11 cubes and 2 smaller cubes of volume 1/8 cubic inch each. Note that the volume of a cube is V = measurement of the side to the third power. Since one side measures 1/2 inch, we get the volume per cube as V = 1/2 inch *1/2 inch * 1/2 inch = 1/8 cubic inch. For the total volume of the rectangular prism, V = no. of cubes* volume per cube; Therefore, V = 90 cubes * 1/8 inch = 11 1/8 cubic inch.
Your answer is: 11 Cubes, and 2 smaller cubes of volume, 1/8 Cubic inch in each.