Exams › SSC CGL (Prelims) › Maths
A boat can go 54 km upstream in 6 hours. If the speed of the stream is 4.8 km/h, then how much time will the boat take to cover a distance of 279 km downstream?
- 20
- 15
- 18
- 16
Correct answer: 15
Solution
Upstream speed is \(54/6=9\) km/h. If stream speed is 4.8 km/h, then boat speed in still water is \(9+4.8=13.8\) km/h. Downstream speed is \(13.8+4.8=18.6\) km/h, so time for 279 km is \(279/18.6=15\) hours.
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