The perimeter of the parallelogram is 20 cm, and one of the sides is 3 cm. Find the lengths of the other sides.

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

So, from the condition it is known that one of the sides of the parallelogram is 3 cm, and its perimeter is 20 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 3 cm.

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

P = 2 (a + b);

2 (3 + x) = 20;

3 + x = 20: 2;

3 + x = 10;

x = 10 – 3;

x = 7 cm is the length of the second pair of sides of the parallelogram.