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):
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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.
