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

• A. P = 4s
• B. A = π r^2
• C. P = 2l + 2w
• D. P = a + b + c

Answer: (C)

Perimeter is the distance around the outside. For a rectangle, you have two sides of length l and two sides of width w, so you add all four sides: l + l + w + w = 2l + 2w. This is the perimeter expression for a rectangle with length l and width w (and it can be written as 2(l + w)). The other expressions don’t describe a rectangle’s perimeter: 4s would be for a square with side s, π r^2 is the circle’s area, and a + b + c is the perimeter of a triangle with sides a, b, and c.