Answer:
120 cubes will fill the box
Step-by-step explanation:
You want to know the number of 1-inch cubes it takes to fill a box that is 5 cubes long, 4 cubes wide, and 6 inches tall.
To cover the bottom of the box, Chan needs to make an array of cubes that has 4 rows with 5 cubes in each row. That layer will have ...
4 × 5 = 20 . . . . cubes per layer
Each layer occupies 1 inch of height, and the box is 6 inches high. The volume of the box will be filled with six of these layers. That will take this many cubes:
(6 layers) × (20 cubes/layer) = 6 × 20 cubes = 120 cubes
Chan will need 120 cubes to fill the box.