A boatman can row 3 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current ?
Select the correct option.
A) 7/2 kmph B) 8/2 kmph C) 5/2 kmph D) 1/2 kmph E) 2/2 kmph
Explanation:   Speed in upstream = Distance / Time = 3 x 60/20 = 9 km/hr.   Speed in downstream = 3 x 60/18 = 10 km/hr   Rate of current = (10-9)/2 = 1/2 km/hr.   Answer: 1/2 kmph
<result>D</result>
A boatman can row 3 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current ?