A boatman can row 3 km against the stream in 20 minutes and return in 12 minutes. Find the rate of current ?
Choose the correct choice:
A) 7/2 kmph  B) 8/2 kmph  C) 5/2 kmph  D) 1/2 kmph  E) 3 kmph
Explanation:   Speed in upstream = Distance / Time = 3 x 60/20 = 9 km/hr.   Speed in downstream = 3 x 60/12 = 15 km/hr   Rate of current = (15-9)/2= 
<gadget id="calculator">(15-9)/2</gadget>
<output>3</output>
3 km/hr.   Answer: 3 kmph
<result>E</result>
A boatman can row 3 km against the stream in 20 minutes and return in 12 minutes. Find the rate of current ?