A boatman can row 3 km against the stream in 20 minutes and return in 15 minutes. Find the rate of current ?  Choose the correct choice:
A) 7/2 kmph	B) 8/2 kmph	C) 5/2 kmph	D) 1.5 kmph	E) 2/2 kmph
Explanation:   Speed in upstream = Distance / Time = 3 x 60/20 = 9 km/hr.   Speed in downstream = 3 x 60/15 = 12 km/hr   Rate of current = (12-9)/2= 
<gadget id="calculator">(12-9)/2</gadget>
<output>3/2 = around 1.5</output>
1.5 km/hr.   Answer: 1.5 kmph
<result>D</result>
A boatman can row 3 km against the stream in 20 minutes and return in 15 minutes. Find the rate of current ?