Question

Sadie computes the perimeter of a rectangle by adding the length, l , and width, w , and doubling this sum. Eric computes the perimeter of a rectangle by doubling the length, l , doubling the width, w , and adding the doubled amounts. (a) Write an expression for Sadie's way of calculating perimeter. Write a different expression for Eric's way. (b) Use both of the expressions to find the perimeter of a rectangle with length 30 and width 75.

Answer 1

a) P = 2(l+w)  Sadie

 P =2l+2w  Eric

b)  Sadie : P = 2(30+75) = 2(105) = 210

Eric: P = 2(30) +2(75) = 60+150 =210