SOLUTION: Sara decides to canoe 3 miles upstream on a river to a waterfall and then come back. Total trip is 6 hours. Sara can canoe at the average speed of 3mph in still water. What is the

Question 435236: Sara decides to canoe 3 miles upstream on a river to a waterfall and then come back. Total trip is 6 hours. Sara can canoe at the average speed of 3mph in still water. What is the speed of the current?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Sara decides to canoe 3 miles upstream on a river to a waterfall and then come back. Total trip is 6 hours. Sara can canoe at the average speed of 3mph in still water. What is the speed of the current?
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Upstream DATA:
distance = 3 miles ; rate = 3-c mph ; time = d/r = 3/(3-c) hrs
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Downstream DATA:
distance = 3 miles; rate = 3+c mph ; time = d/r = 3/(3+c) hrs
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Equation:
time + time = 6 hrs.
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3/(3-c) + 3/(3+c) = 6
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1/(3-c) + 1/(3+c) = 2
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(3+c) + (3-c) = 2(9-c^2)
6 = 2(9-c^2)
3 = 9-c^2
c^2 = 6
c = sqrt(6) (speed of the current)
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Cheers,
Stan H.
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