Question

Given the perimeter of a rectangle and either the length or​ width, find the unknown measurement using the appropriate formula.

The perimeter is 76 cm and the length is 20 cm.
What is the width of the rectangle? Show all your work.

Answer 1

$p = 2l + 2w$
P=Perimeter
L=Length
W=Width

Hints given are P= 76, L=20 so 2L=40

76=40+2w
76-40=2w
36=2w
18=w

Answer 2

The formula of a perimeter of a rectangle:

P = 2(w + l)

We have P = 76 cm and l = 20 cm.

Substitute:

2(w + 20) = 76       use distributive property

(2)(w) + (2)(20) = 76

2w + 40 = 76     subtract 40 from both sides

2w = 36       divide both sies by 2

w = 18

Answer: the width = 18 cm