If one side of a square is reduced by 20%, then its perimeter will decrease by 12 cm. Calculate the side of this square.

It is known that the perimeter of a square is the sum of the lengths of all its sides. The square has 4 sides. In this case, this means that if the side of the square is reduced by 20%, then its length will decrease by:

12: 4 = 3 centimeters.

Let’s take for x – the length of the side of the square. Let’s solve the problem using the proportion method:

20% – 3 cm

100% – x cm

The proportion is straight, we express x:

x = 3 * 100: 20 = 15 cm – the original length of the side of the square.

Answer: The original length of the side of the square is 15 centimeters.