The area of the rectangle is 40 dm², and one of the sides is 50 cm. Calculate the perimeter of the rectangle.

In order to find the perimeter of a rectangle, you need to know the lengths of its sides.

We know an area equal to 40 dm² and a side = 50 cm = 5 dm (since 1 dm = 10 cm). Let us express the unknown side from the area formula:

If S = a * b, therefore:

a = S: b = 40: 5 = 8 dm.

Perimeter is the sum of all sides. Let’s find it by the formula:

P = 2a + 2b = 2 * 5 + 2 * 8 = 10 + 16 = 26 dm.