SOLUTION: A man rowed 16 km upstream in 4 hours. If the river flowed with a current of 2 kph, how long did the man's return trip take?

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Question 982639: A man rowed 16 km upstream in 4 hours. If the river flowed with a current of 2 kph, how long did the man's return trip take?
Answer by ikleyn(52803)   (Show Source): You can put this solution on YOUR website!

Let  u  be the rower's speed in still water in kilometers per hour  ().
Since the river floats with a current of  2 ,  the rower's speed is  u-2  relative to the bank of the river,  when the man rows upstream.  It gives you an equation
= .

Hence,  u - 2 = = 4 .
Therefore,  u = 4 + 2 = 6  (the rower's speed in still water).
It implies that the rower's speed is  u+2 = 6 + 2 = 8  relative to the bank of the river,  when the man rows downstream.

It means that the way downstream will take   = 2 hours.

Answer. The return trip will take  2  hours.


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