Q. A boy can swim in still water at a speed of 10 km/hr. If the speed of the current would have been 5kmph, then the boy could swim 60 km
Answer: downstream in 4 hours
Notes: Rate downstream = 10 + 5 = 15 kmph Rate upstream = 10 - 5 = 5 kmph Time taken in swimming 60 km downstream = $latex \frac{60}{15} = 4hours&s=1$ Time taken in swimming 60 km upstream = $latex \frac{60}{5} = 12hours&s=1$ From, given options, boy can swim 60km downstream in 4 hrs. So option [B] is the right answer.

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