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?

A 1 hour 12 min Correct Answer Incorrect Answer
B 1 hour 10 min Correct Answer Incorrect Answer
C 1 hour 50 min Correct Answer Incorrect Answer
D 2 hour 30 min Correct Answer Incorrect Answer

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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