Question
Speed of a boat in still water is 9 km/hr. It goes 12 km
downstream and comes back to the starting point in three hours. What is the speed of water in the stream?Solution
Let the speed of the boat = 9km/hr Speed of current = x km/hr Speed upstream = (9 – x) km/hr Speed downstream = (9 + x) km/hr Time upstream + time downstream = 3 hours Time  = distance/(speed ) 12/(9-x)+  12/(9+x) = 3 x = 3 km/hrÂ
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