Question

Suppose that a rectangular piece of glass has a perimeter of 20 meters. If we multiply both its length and its width by 4, what will be the perimeter

of the new rectangular piece of glass?
A) 65 m
B) 80 m
C) 34 m
D) 45 m

Answer 1

B) 80 m

Explanation:

Let W = width

Let L = length

perimeter of a rectangle = 2 x width + 2 x length = 2(W + L)

If the perimeter of a rectangle = 20 m

⇒ 2(W + L) = 20

If we multiply both its length and width by 4:

Width = 4W

Length = 4L

⇒ perimeter = 2(4W + 4L) = 8(W + L)

As 2(W + L) = 20

Then 8(W + L) = 4 x 2(W + L) = 4 x 20 = 80 m