Perimeter Formula

by Calum
(U.K)

The length of a rectangle is 4 times the width.
The perimeter of the rectangle is 80cm.
Find the length of each side.

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Sep 16, 2010
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Perimeter Formula
by: Karin

Hi Calum,

For this problem, you must know from prior knowledge that the formula for perimeter of a rectangle is: 2L + 2W = P.

We know the length is 4 times the width, but we don't know the width, so we are going to assign a variable to the width.

Let w = width of the rectangle
L = 4w
Therefore, the length is 4w. (4 times the width)

Now we'll substitute.

2L + 2W = P
2(4w) + 2w = 80

Now we'll simplify and solve for w.

8w + 2w = 80
10w = 80

10w/10 = 80/10

w = 8

The width is 8 cm and the length is 4 times the width which is 32 cm.

I hope this helps,
Karin

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