The difference between the two sides of the parallelogram is 20 cm. Find the sides of the parallelogram if P = 80 cm.

In order to find the lengths of the sides of a parallelogram, using the formula for finding the perimeter of a parallelogram, we will compose and solve the equation.

The condition says that the difference between the two sides of the parallelogram is 20 cm. It is also known that the perimeter of the parallelogram is 80 cm.

We denote by x cm the length of one of the sides, then we write the length of the second side as (x – 20) cm.

P = 2 (a + b);

We get the equation:

2 (x + (x – 20)) = 80;

x + x – 20 = 40;

2x = 40 + 20;

2x = 60;

x = 30 cm length of one side and 30 – 20 = 10 cm length of the second side.