Question

The perimeter of a rectangle is 10 feet, and the area is 6 square feet. What is the width of

the rectangle?

Answer 1

Hello,

Perimeter of a rectangle : 2 * (length + width)

Area of a rectangle : length * width

We know that the perimeter of the rectangle is equal to 10 feet and its area is equal to 6 square feet.

Let's call x the length of the rectangle and y the width of the rectangle. The pair (x ; y) verifies the following system :

2 (x + y) = 10 ⇔ x + y = 5 ⇔ x = 5 - y

x * y = 6 ⇔ (5 - y) * y = 6 ⇔ 5y - y² - 6 = 0 ⇔ y² - 5y + 6 = 0

⇔ y² - 3y - 2y + 6 = 0 ⇔ y(y - 3) - 2(y - 3) = 0 ⇔ (y - 2)(y - 3) = 0

⇔ y = 2 ou y = 3

x = 5 - y ⇔ x = 5 - 2 or x = 3 - 2 ⇔ x = 3 or y = 2

S = {(3 ; 2) ; (2 ; 3)}

The width of the rectangle is 2 or 3 feet.

:-)