The sides of the rectangle are 12 cm and 8 cm. Find the side of the square that has the same perimeter as the given rectangle.

To solve this problem, remember that the perimeter of a rectangle is the sum of the lengths of all its sides. Since in a rectangle the opposite sides are equal, then P = 2 * (a + b), where a is the length, b is the width. Knowing that the sides are 12 cm and 8 cm, we calculate the perimeter.

P = 2 * (12 + 8) = 2 * 20 = 40 centimeters.

The perimeter of a square is equal to the sum of the lengths of all its four sides. Since all sides of a square are equal, its perimeter P = 4a, where a is its side. Knowing that the perimeter is 40 centimeters, we calculate the length of the side.

a = 40/4 = 10 cm.

Answer: 10 cm.