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.