The length of a rectangle is 20 mm longer than its width, find the lengths of the sides of this rectangle

The length of a rectangle is 20 mm longer than its width, find the lengths of the sides of this rectangle if its perimeter is 12 cm.

Let’s denote the width of the rectangle by x mm.

By condition, the length of the rectangle is 20 mm longer than the width, that is, the length of the rectangle is x + 20 mm.

Let’s compose and solve the equation if the perimeter, that is, the doubled sum of the two sides of the rectangle is 12 cm or 120 mm:

2 (x + x + 20) = 120.

2 x + 2 x + 40 = 120.

4 x = 120 – 40.

4 x = 80.

x = 80: 4.

x = 20.

Thus, the width of the rectangle is 20 mm.

Find the length: 20 + 20 = 40 (mm).

Answer: the length of the rectangle is 40 mm, the width is 20 mm.