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

the width is 18.

step by step:
1. 2 lengths are 20 which is 20+20 that's 40.
2. 76-40= 36
3. Two widths are 36 cm.
4. so do 36÷2 and that equals 18

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