The side of an equilateral triangle is 8 cm. Find the area of a square whose perimeter is equal to the perimeter of this triangle.

First, we find what the perimeter of this triangle is equal to.

Since, according to the condition of the problem, the triangle is equilateral, its perimeter will be equal to

P = 3 * a, where a is the length of the side of the triangle.

Therefore, P = 3 * 8 = 24 (cm).

The perimeter of the square is P = 4 * a, where a is the length of the side of the square. We get:

24 = 4 * a, so a = 24: 4 = 6 (cm).

The area of the square is S = a², where a is the length of the side of the square, so the area of our square is S = 6² = 36 (cm²).

Answer: S = 36 cm².