A boat goes 60 km downstream whose speed is 15 km/hr in still water and comes back to the origin in a total of 9 hours. Find the speed of the stream :
Let the speed of the stream be x kmph. Then,
Speed Downstream = (15+x) kmph,
Speed Upstream = (15-x) kmph.
.'. 60/(15+x) + 60/(15-x) = 9
=> 1800/(225 - x^2) = 9
=> x = 5 kmph.
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