Question
A boat can cover 84 km upstream and 252 km downstream in
14 hours. Speed of the stream is how much less than the speed of the boat in still water if the boat can cover 63 km upstream and 189 km downstream in 10 hours?Solution
ATQ, ATQ, Let the upstream speed and downstream speed of the boat be x km/h and y km/h, respectively. So according to question: 84/x + 252/y = 14 ………………. (i) Also, 63/x + 189/y = 10 ……….. (ii) Solving (i) and (ii), we get x = 14 and y = 42 So, the upstream speed and downstream speed of the boat are 14 km/h and 42 km/h, respectively. Speed of the boat in still water = (14 + 42)/2 = 28 km/h Speed of the stream = (42 – 14)/2 = 14 km/h So, the desired difference = 28 – 14 = 14 km/h
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