A man rows to a place 30 km distant and back in 25 hours. He finds that he can row 6 km with the stream in the same time as 4 km against the stream. The rate of the stream is :
Suppose he moves 6 km downstream in x hours. Then,
Speed downstream =6/x km/hr, speed upstream = 4/x km/hr.
.'. 30/(6/x) + 30/(4/x) = 25
or x = 2.
so, speed downstream = 3 km/hr,
speed upstream = 2 km/hr.
rate of the stream = (4-3)/2 = 1/2 km/hr.
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