A man wishes to cover a 1 km distance in river water. In still water he takes 12 minutes to cover it, but in the flowing river, he takes 13 minutes. The speed of the flowing water of the river is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. km/hr.
We know that,
Speed = Distance/Time
Now,
Speed in still water = 1 km/12 min
⇒ 1 km/(12/60 hrs) = 1 km/ 0.2 hrs = 5 km/hr
Now,
Speed in flowing water = 1km/13 min
⇒ 1 km/(13/60 hrs) = 1 km/0.2167 hrs ≈ 4.615 km/hr
Now,
Speed in river flow = Speed in still water - speed in flowing water
⇒ 5 - 4.615
⇒ 0.385 = km/hr