SOLUTION: A boat can travel at a speed of 12km / h in still water. If it takes three hours to go 15km upstream and back, find the speed of the current.

Question 574816: A boat can travel at a speed of 12km / h in still water. If it takes three hours to go 15km upstream and back, find the speed of the current.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A boat can travel at a speed of 12km / h in still water. If it takes three hours to go 15km upstream and back, find the speed of the current.
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Upstream DATA:
rate = 12-c km/h ; distance = 15 km ; time = 15/(12-c) hrs
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Downstream DATA:
rate = 12+c km/h ; distance = 15 km ; time = 15/(12+c) hrs
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Equation:
time + time = 3 hrs.
15/(12-c) + 15/(12+c) = 3
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[15(12+c) + 15(12-c) = 3(144-c^2)
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360 = 3(144-c^2
120 = 144-c^2
c^2 = 24
c = 2sqrt(6) km/h (speed of the current)
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Cheers,
Stan H.
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