Question

A sandbox has a perimeter of 21 1/2 feet. If the length is 5 1/4 feet, what is the area of the sand box?

Answer 1

The perimeter of a rectangle is twice the sum of length and width, so the sum of length and width is half the perimeter, 10 3/4 ft.

The width will be the difference between this and the length, hence 5 1/2 ft.

The area is the product of length and width.
  A = length×width
  A = (5.25 ft)×(5.5 ft) = 28.875 ft²

The area of the sandbox is 28 7/8 ft².