The perimeter of the rectangle is 56 cm, the length is 3 times the length.

From the condition it is known that the perimeter of the rectangle is 56 cm, and it is also known that the length of the rectangle is 3 times the width. In order to find the length of the rectangle, we will compose and solve the equation.

Let’s start by using the variable x cm for the width of the rectangle, while the length can be written as 3x cm.

To find the perimeter, we will use the formula:

P = 2 (a + b);

2 (x + 3x) = 56;

x + 3x = 56: 2;

x (1 + 3) = 28;

4x = 28;

x = 28: 4;

x = 7 cm width of the rectangle and 7 * 3 = 21 cm length.