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The length of a rectangle is twice it's width. If it's perimeter is 54cm, find its length. Explain!

remember the formulas:

Area = length * width

Perimeter = 2 * length + 2 * width

therefore 54 = 2l + 2w and length is 2 * width or l = 2w

54 = 2* (2w) + 2w

54 = 4w + 2w

54 = 6w

54/6 = w

9 = w and

l = 2*9

l = 18

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