What is the area of a square with a perimeter of 20 cm?

To solve this problem, remember that the perimeter of a square is equal to the sum of the lengths of its four sides. Since all 4 sides of a square are equal, the perimeter of the square is P = 4a, where a is the side of the square. We calculate the length of the side, knowing that the perimeter is 20.
a = 20/4 = 5 cm.
Recall that the area of a square is equal to the square of its side.
S = 5 * 5 = 25 cm ^ 2.
Answer: 25 cm ^ 2.