A man can row 15 km/hr in still water. It takes him twice as long row up as to row down the river. Find the rate of stream.
Let man's rate upstream be x km/hr. then, his rate downstream - 2x km/hr
.'. Rate in still water = 1/2(2x + x) = 3x/2 km/hr.
so, 3x/2 = 15
=> 3x = 30
=> x = 10 km/hr
Rate upstream = 10 km/hr
Rate downstream = 2*10 = 20 km/hr.
hence, rate of stream = 1/2(20 -10)
= 5 km/hr.
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