Which expression gives the area of a rectangle with length l and width w?

Which expression gives the area of a rectangle with length l and width w?

• A. a = 1/2 b h
• B. a = l × w
• C. p = 2(l + w)
• D. a = l + w

Answer: (B)

Area is the amount of space inside a shape. For a rectangle with length l and width w, you can think of filling the shape with unit squares. There would be l rows of w squares each, so the total number of unit squares is l × w. That product exactly counts how much space is inside, so the area is a = l × w. The other expressions describe different things: 1/2 b h is the area of a triangle, 2(l + w) is the perimeter, and l + w isn’t an area measure.

Area is the amount of space inside a shape. For a rectangle with length l and width w, you can think of filling the shape with unit squares. There would be l rows of w squares each, so the total number of unit squares is l × w. That product exactly counts how much space is inside, so the area is a = l × w. The other expressions describe different things: 1/2 b h is the area of a triangle, 2(l + w) is the perimeter, and l + w isn’t an area measure.