The perimeter of the parallelogram is 80, one of its sides is 4 times the other. Find the smaller side of the parallelogram.

The perimeter of the parallelogram is found by the formula: P = 2 (a + b). Let the smaller side of the parallelogram be “x”, since the larger side is 4 times larger than the smaller, then we will designate it as “4x”. We know that the perimeter of the parallelogram is 80, then we write all the known data into the formula for finding the perimeter. 2 (4x + x) = 80; 2 * 5x = 80; 5x = 80: 2; 5x = 40; x = 40: 5; x = 8. So the smaller side is 8.
Answer: 8.