Answer:
To fill your box with one inch cubes first cover the bottom. This takes 48 rows of small cubes, each row containing 72 cubes. Thus to cover the bottom takes 48 x 72 = 3456 cubes. Since your box is 6" high you need 6 layers of 3456 cubes or 6 x 3456 = 20736 cubes to fill the box.
