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A boatman goes $2$ km against the current of the stream in $1$ hour and goes $1$ km along the current in $10$ minutes. How long will it take to go $5$ km in stationary water?

1. $40$ minutes
2. $1$ hour
3. $1$ hr $15$ min
4. $1$ hr $30$ min

let s = boatman’s speed in still water , r = river’s flow(speed)

s+r = 2 kmph (speed = distance/time)

s-r = 6 kmph(convert time given in minutes into hour)

thus , s=4kmph

hence, time = 5/4 hrs = 1.25 hr = 1 hour 15 minutes
58 points

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