The perimeter of the rectangle is 20cm. Its width is 3cm. What is the length of this rectangle?

The perimeter of a rectangle is the sum of the length and width times two.

The first way.

1. Determine what the length of the rectangle is equal to.

(20 – 3 * 2) / 2 = (20 – 6) / 2 = 14/2 = 7 centimeters.

Answer: The length of the rectangle is 7 centimeters.

Second way.

We will solve the problem using an equation with one unknown.

1. The length of the rectangle is x centimeters.

2. Let’s compose and solve the equation.

(x + 3) * 2 = 20;

2x + 6 = 20;

2x = 20 – 6 = 14;

x = 14/2 = 7;

x = 7;

Answer: The length of the rectangle is x = 7 centimeters.