Question
The speed of a boat in still water and the speed of the
stream are in the ratio 7:2. If the boat takes 12 hours to travel 240 km upstream, how long will it take the boat to travel 144 km downstream?Solution
Let speed of boat in still water and speed of stream be '7x' km/hr and '2x' km/hr, respectively. So, upstream speed of boat = 7x - 2x = '5x' km/hr ATQ, (240/5x) = 12 Or, 'x' = 4 So, downstream speed of the boat = 7x + 2x = 9x = 9 X 4 = 36 km/hr Therefore, required time = (144/36) = 4 hours
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