If your area is big enough, counting square units could take all day! Luckily, there’s a formula to help us find the area of squares and rectangles a lot faster. Multiplying the length of the square or rectangle by the width will give you the same answer as adding up all the square units. But don’t try to use this formula to find the area of a triangle or circle. The l × w formula only works to find the area of squares and rectangles. A rectangle has a length of 20 units and a width of 15 units. Which of the following number sentences would you use to find the area of the rectangle?

A
20 + 15

B
20 - 15

C
20 x 15

D
20 ÷ 15