Question
A boat can travel 30 km downstream in 45 min. The ratio
of the speed of the boat in still water to the speed of the stream is 5: 3. How much time will the boat take to cover 25 km upstream?Solution
Speed of downstream = D/T = 30 × (60/45) = 40 km/hr The ratio of the speed of the boat in still water to the speed of the stream = 5: 3 (5x, 3x) => 8x = 40 => x = 5 Speed of upstream = 5x – 3x = 2x = 10 km/hr Distance = 25 km Time = D/S = 25/10 = 2(1/2) hr = 2-hour 30 min
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