SOLUTION: A tank may be filled using pipe A and B with times of 12 and 20 minutes respectively. It takes only 5 minutes to fill the tank when pipe C is used simultaneously with pipes A and B

Question 646084: A tank may be filled using pipe A and B with times of 12 and 20 minutes respectively. It takes only 5 minutes to fill the tank when pipe C is used simultaneously with pipes A and B. How long does it take to fill the tank using only pipe C?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A tank may be filled using pipe A and B with times of 12 and 20 minutes respectively. It takes only 5 minutes to fill the tank when pipe C is used simultaneously with pipes A and B. How long does it take to fill the tank using only pipe C?
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A rate = 1/12 job/min
B rate = 1/20 job/min
C rate = 1/x job/min
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Equation:
rate + rate + rate = together rate
1/12 + 1/20 + 1/x = 1/5
----
5x + 3x + 60 = 12x
4x = 60
x = 15 minutes (time for C to fill the tank alone)
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Cheers,
Stan H.
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