The perimeter of a rectangle is 120 cm. Find the lengths of its sides if one of them is half the length of the other.

If the perimeter of the rectangle is 120 cm, then the sum of the lengths of all four sides is 120 cm.

Since the sides of the rectangle are pairwise equal, we can say another way – the perimeter of the rectangle is equal to twice the sum of the length and width measurements.

Let’s denote the sides of the rectangle equal:

2 * X and X (X is the side that is half as long),

Then the perimeter of the rectangle can be written as follows:

P = 2 * X + X + 2 * X + X = 6 * X = 120;

X = 120/6 = 20 cm.

That is, the short side is 20 cm.

Find the long side (it is twice as long):

2 * X = 2 * 20 = 40 cm.

Answer: the sides of the rectangle are 40 cm and 20 cm.