SOLUTION: I'm having trouble with this word problem, please help :) The length of a certain lot is 20 feet less than four times its width. The area is 4200 sq. ft. What are the dimensions

Question 487863: I'm having trouble with this word problem, please help :)
The length of a certain lot is 20 feet less than four times its width. The area is 4200 sq. ft. What are the dimensions of the lot?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The length of a certain lot is 20 feet less than four times its width. The area is 4200 sq. ft. What are the dimensions of the lot?
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Let the width be W.
Then the length is 4W-20
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Equation:
Area = length*width
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W(4W-20) = 4200
4W^2 - 20W - 4200 = 0
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W^2 - 5W - 1050 = 0
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Factor:
W = [5 +- sqrt(25 - 4*-1050)]/2
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W = [5 +- sqrt(4225)]/2
W = [5 +- 65]/2
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Positive solution:
W = 35 (width)
Length = 4*35-20 = 120
==============
Cheers,
Stan H.
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