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Question 675257: Two pipes are used to fill a water storage tank. The first pipe can fill the tank in 4 hours, and the two pipes together can fill the tank in 2 hours less time than the second pipe alone. How long would it take for the second pipe to fill the tank?
If you could solve in quadratics, that would be best.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Two pipes are used to fill a water storage tank. The first pipe can fill the tank in 4 hours, and the two pipes together can fill the tank in 2 hours less time than the second pipe alone. How long would it take for the second pipe to fill the tank?
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1st pipe rate is 1/4 job/hr
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2nd pipe rate is 1/x job/hr
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Together rate is 1/(x-2) job/hr
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Equation:
rate + rate = together rate
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1/4 + 1/x = 1/(x-2)
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x(x-2) + 4(x-2) = 4x
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x^2 - 2x + 4x-8 = 4x
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x^2 -2x - 8 = 0
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Factor:
(x-4)(x+2) = 0
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Positive solution:
x = 4 hrs (time for the 2nd pipe to do the job)
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x-2 = 2 hrs (time for the 2 pipes to do the job together)
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Cheers,
Stan H.
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