Recall the formula for finding the area of a rectangle:
Area = Length × Width
Recall the formula for finding the perimeter of a rectangle:
Perimeter = 2 ( Length + Width )
Given in your problem:
Area = 40 sq. units
Perimeter = 26 units
Required to solve for:
Length (L) and width (W)
• First, substitute the given to the formula:
Area = Length x Width
40 = L × W ⇒ equation number 1
Perimeter = 2 ( Length + Width )
26 = 2 ( L + W ) ⇒ equation number 2
• Simplifying equation number 2,
13 = L + W
• Rearranging the equation,
L = 13 - W ⇒ equation 3
Substituting equation 3 from equation 1:
( equation 1 ) 40 = (L)(W)
( equation 3 ) L = 13 - W
40 = (13 - W) (W)
40 = 13W - W²
( regrouping ) W² - 13W + 40 = 0
( factoring ) (W - 8) (W - 5) = 0
W - 8 = 0 ; W - 5 = 0
W = 8 ; W = 5
Therefore, there are 2 possible values for the width of the rectangle. It can be 8 units or 5 units.
• Now to solve for the length of the rectangle, substitute the two values of width to equation 3.
(equation 3) L = 13 - W
for W = 8 ⇒ L = 13 - 8
L = 5 units
for W = 5 ⇒ L = 13 - 5
L = 8 units