SOLUTION: It takes 12 hours to fill a swimming pool using two pipes. If the pipe of larger diameter is used for 4 hours and the pipe with smaller diameter for 9 hours, only half the tank is

Algebra ->  Rate-of-work-word-problems -> SOLUTION: It takes 12 hours to fill a swimming pool using two pipes. If the pipe of larger diameter is used for 4 hours and the pipe with smaller diameter for 9 hours, only half the tank is       Log On


   

Question 453419: It takes 12 hours to fill a swimming pool using two pipes. If the pipe of larger diameter is used for 4 hours and the pipe with smaller diameter for 9 hours, only half the tank is filled. How long would it take for each pipe to fill the pool separately ?
Please help !!!
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
It takes 12 hours to fill a swimming pool using two pipes. If the pipe of larger diameter is used for 4 hours and the pipe with smaller diameter for 9 hours, only half the tank is filled. How long would it take for each pipe to fill the pool separately ?
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Let larger pipe rate be x hrs/job
Let smaller pipe rate be y hrs/job
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Equations:
x + y = 1/12
4x+9y = 1/2
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Modify to get:
24x + 24y = 2
24x + 54y = 3
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Subtract and solve for "y":
30y = 1
y = 1/30 job/hr (rate of the smaller diameter pipe)
Smaller pipe would take 30 hrs to fill the pool.
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Solve for "x"
x + (1/30) = 1/12
x = (1/12)-(1/30)
x = (18/(12*30)) = 1/20 job/hr
Larger pipe would take 20 hrs to fill the pool.
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Cheers,
Stan H.