A rectangular room is 12 feet long and 9 feet wide. How many square feet of carpet are needed to cover the floor?

The area of a rectangle is length × width. Here area = 12 ft × 9 ft = 108 square feet. Carpeting a floor is an area problem, so you multiply the two dimensions. Be careful not to confuse area with perimeter: the perimeter (distance around) would be 2 × (12 + 9) = 42 feet, which is offered as a distractor. Square footage of a floor is always length times width. The room needs 108 square feet of carpet.