The length of a rectangle is five times its width. If the area of the rectangle is 405 cm^2 find its perimeter

Question

Finding the perimeter 

Answer 1

The area is the length times width.  The perimeter is the sum of twice the length and twice the width.

 

Let width = x

Let length = 5x

 

First, we create an equation to represent the area.  This will allow us to solve for x.

 

x(5x) = 405

 

5x² = 405

 

 

Divide both sides of the equation by 5.

 

x² = 81

 

 

Square-root both sides of the equation.

 

x = 9

 

 

If this is the width, then length is 5 times 9.

 

width = 9 cm

length = 45 cm

 

 

Perimeter = 2 * (9 cm + 45 cm)