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| Math Central | Quandaries & Queries |
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Question from Josh, a student: Dave and Jane have a new rectangular driveway. The perimeter of the driveway is 168 feet. The length is 12 feet longer than three times the width. What are the dimensions of the driveway? |
Josh,
Suppose the length of the driveway is L feet and the width is W feet. The perimeter is 168 feet so walking around the driveway and measuring the sides gives
L + W + L + W = 168 feet.
or just going half way around
L + W = 84.
This can be rewritten
L = 84 - W.
Now look at the sentence "The length is 12 feet longer than three times the width." If the width is W feet what is 3 times the width? What is 12 feet more than three times the width? This is the length so now you have a second expression for L. Set the two expressions equal to each other and solve for W.
I hope this helps,
Penny
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