Question
A man can row at a speed of 20 km/hr in still water to a
certain upstream point and back to the starting point in a river which flows at 5 km/hr. Find his average speed for total journey.Solution
Speed of the man in still water = 20 km/hr Speed of the stream = 5 km/hr Speed downstream = (20 + 5) = 25 km/hr Speed upstream = (20 - 5) = 15 km/hr Average speed = (Speed downstream x Speed upstream)/Speed in still water = (25 x 15)/20 = 18.75 km/hr
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