Question
A boat can travel 12 km upstream in 30 min. If the ratio
of the speed of the boat in still water to the speed of the stream is 5:1, how much time will the boat take to cover 15 km downstream?Solution
Speed ratio = 5x : 1x. Downstream = 6x; upstream = 4x. Upstream speed = 12 km / 0.5 hr = 24 kmph. 4x = 24, x = 6. Downstream speed = 6x = 36 kmph. Time taken for 15 km downstream = 15 km/36 kmph = 25 min.
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