Question 565105: A boy can row a boat at a constant rate of 5 mi/hr in still water, as indicated in the figure. He rows upstream for 20 minutes and then rows downstream, returning to his starting point in another 12 minutes. Find the rate of the current.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A boy can row a boat at a constant rate of 5 mi/hr in still water, as indicated in the figure. He rows upstream for 20 minutes and then rows downstream, returning to his starting point in another 12 minutes. Find the rate of the current.
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Upstream DATA:
time = 1/3 hr ; rate = (5-c) mph ; distance = t*r = (1/3)(5-c) miles
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Dowmstream DATA:
time = 1/5 hr ; rate = (5+c) mph ; distance = t*r = (1/5)(5+c) miles
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Equation:
distance = distance
(1/3)(5-c) = (1/5)(5+c)
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Multiply both sides by 15:
5(5-c) = 3(5+c)
25-5c = 15+3c
8c = 10
c = 5/4 mph (speed of the current)
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Cheers,
Stan H.
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