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A boat which travels at the rate of 10.5 km/hr downstream takes 3 times as long time to go to a certain distance up a river as to go the same distance down. Find the rate at which stream flows. |
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Answer» Let the speed of stream = x km/hr and the speed of boat in still water = y km/hr `therefore` Speed of boat downstream = (x + y) km/hr and speed of boat upstream = (y - x) km/hr Let the distance be D km. `therefore` According to the problem, x + y = 10.5 ...(1) Also, time taken by boat upstream = 3 `xx` time taken by boat downsteam implies `(D)/(y - x) = 3 xx (D)/(10.5)` `implies y - x = 3.5` Adding equations (1) and (2), we get 2y = 14 implies y = 7 Putting y = 7 in equation (1), we get x + 7 = 10.5 implies x = 3.5 Hence, speed of stream = 3.5 km/hr |
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