Question
A boat can travel 225 km
downstream in 5 hours. If the speed of the boat in still water is 7 times the speed of the stream, how much time will it take for the boat to cover 84 km upstream?Solution
ATQ, Let the speed of the stream be 'x' km/hr Therefore, speed of the boat in still water = 'x' + 7x = '8x' km/hr According to the question, Downstream speed of the boat = 8x + x = (225/5) = 45 Or, 9x = 45 Or, x = (45/9) = 5 Therefore, upstream speed of the boat = 8x - x = 7x = 7 X 5 = 35 km/hr Therefore, required time taken = (84/35) = 2.4 hours
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