What are the dimensions of the original poster?

Question

Ace made a poster for Easter. The length of the poster is 3 more than the width. If the length of the

poster is doubled and the width is increased by 5, the perimeter of the old rectangle is increased by 40

inches. What are the dimensions of the original poster?

Answer 1

L =3+W

original perimeter = 2L +2W = 2(3+W) +2W = 6 +4W

new perimeter = 2(2L) + 2(W+5) = 2(2)(3+W) + 2W +10 = 12+4W +2W +10 = 22+6W

increase = 22+6W - (4W+6) = 2W +16 = 40

2W =24

W =24/2 = 12

W = 12 inches wide

L = 15 inches long

original perimeter =2(12+15) = 2(27) = 54 in^2

new perimeter = 2(30+17) = 2(47) = 94 in^2

dimensions of the original poster are 12 inches by 15 inches