One side of the rectangle is 40 cm, and its perimeter is 210 cm. Calculate the area of the rectangle?

We denote the length of the second side of the rectangle through the variable X.

Let’s compose and solve an equation with one unknown X according to the condition of our problem.

2 x 40 + 2 x X = 210.

80 + 2 x X = 210.

2 x X = 210 – 80.

2 x X = 30.

X = 30: 2.

X = 15.

We get that the length of the second side of the rectangle is 15 cm.

To find the area of a rectangle, multiply the lengths of its sides.

40 x 15 = 600.

Thus, the area of our rectangle is 600 square meters. cm.