Question
A man can row 6 km/hr in still water. It takes him twice
as long to row up as to row down the river. Find the rate of the stream.Solution
Let stream speed = y. Boat speed = 6. Downstream speed = 6 + y. Upstream speed = 6 - y. Time Up = 2 × Time Down. Since Distance is constant, Speed is inversely proportional to Time. Speed Down = 2 × Speed Up 6 + y = 2(6 - y) 6 + y = 12 - 2y 3y = 6 y = 2 km/hr.
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