A man can row upstream at 10kmph and downstream at 20kmph. Find man's rate in still water ?	Pick one:  A) 5km/hr  B) 15km/hr  C) 10km/hr  D) 20km/hr  E) 7.5km/hr
Rate in still water = 1/2 (10+20) = 15km/hr   Answer is 15km/hr
<result>B</result>
A man can row upstream at 10kmph and downstream at 20kmph. Find man's rate in still water ?