Explanation:
The floor area is also the bottom area, and the bottom area is the area where the bottom surface contacts the ground. The bottom of a cuboid is a rectangle: length * width. If a cuboid is in space, its dimensions are length * width * height.
When a cuboid is placed on the ground, its length, width or height may be in contact with the ground. The calculation at this time is that the product of the length and width of the surface in contact with the ground is the bottom area of the cuboid! In a word, multiply the length and width of the ground contact surface to get the floor area of the cuboid.
Expand:
The area formula of a cuboid is: length times width.
The volume formula of a cuboid is: length times width times height.