SOLUTION: A college crew team can maintain a speed equivalent to 15 km/hr in still water. If it takes the team 50 minutes to row 6 km upstream and back, what is the rate of the current in th

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Question 439292: A college crew team can maintain a speed equivalent to 15 km/hr in still water. If it takes the team 50 minutes to row 6 km upstream and back, what is the rate of the current in the river?
my teacher gave me the answer 3km/hr but i cant figure out how to set it up. could you also explain as you go through? thank you very much :D
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A college crew team can maintain a speed equivalent to 15 km/hr in still water. If it takes the team 50 minutes to row 6 km upstream and back, what is the rate of the current in the river?
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upstream DATA:
distance = 6 km ; rate = 15-c ; time = d/r = 6/(15-c) hrs.
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downstream DATA:
distance = 6 km ; rate = 15+c ; time = d/r = 6/(15+c) hrs
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Equation:
time + time = (5/6) hr
6/(15-c) + 6/(15+c) = (5/6) hr
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6*6(15+c) + 6*6(15-c) = 5*(225-c^2)
1080 = 5(225-c^2)
216 = 225-c^2
c^2 = 9
Positive solution:
c = 3 km/hr (speed of the current)
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Cheers,
Stan H.
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my teacher gave me the answer 3km/hr