Question 311925
Two pipes can fill a large tank in 10 hours. One of the pipes, used alone, takes 15 hours longer than the other to fill the tank. How long would each pipe take to fill the tank alone? 
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Together Data:
time = 10 hrs/job ; rate = 1/10 job/hr
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One-Pipe Data:
time = x+15 hrs/job ; rate = 1/(x+15) job/hr
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Other-Pipe Data:
time = x hrs/job ; rate = 1/x job/hr.
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Equation:
rate + rate = together rate
1/x + 1/(x+15) = 1/10
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10(x+15) + 10x = x(x+15)
20x + 150 = x^2 + 15x
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x^2 - 5x - 150 = 0
(x-15)(x+10) = 0
Positive solution:
x = 15 hrs (time for one of the pipe)
x+15 = 30 hrs (time for the other pipe)
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Cheers,
Stan H.