Q. A boat running downstream covers a distance of 20 km in 2 hrs while it covers the same distance upstream in 5 hrs. Then speed of the both in still water is
Answer: 7 km/hr
Notes: Let the speed of boat in still water be x kmph and that of stream be y kmph. $latex \therefore \frac{20}{x+y} = 2&s=1$ $latex => x+y = 10$ …….(1) $latex \frac{20}{x-y} = 5&s=1$ $latex => x-y = 4$............(2) On adding, 2x = 14 kmph = 7 kmph Hence option [C] is the right answer.

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