The perimeter of the parallelogram is 56 cm. One of its sides is 7 cm. Find the second one.

In order to find the sides of a parallelogram, we will recall the properties of the sides of a rectangle and the formula for finding the perimeter of a rectangle.

So, from the condition it is known that one of the sides of the parallelogram is 7 cm, and its perimeter is 56 cm.

Opposite sides of a parallelogram are equal to each other. That is, the length of one pair of sides is known to us as 7 cm.

Let’s denote by x cm the length of the second side.

P = 2 (a + b);

2 (7 + x) = 56;

7 + x = 56: 2;

7 + x = 28;

x = 28 – 7;

x = 21 cm length of the second pair of sides of the parallelogram.