The length of a rectangle is three times its width. If the perimeter of the rectangle is 48, what is its area?
The perimeter of a rectangle is l + w + l + w = 48. Since l = 3w, the perimeter is 3w + w + 3w + w = 48 so 8w = 48 and w = 6. Therefore, the length is 3 × 6 or 18 and the area of the rectangle is l × w = 18 × 6 = 108.