Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes at 13 km/hr downstream and 4 km/hr upstream.  Select: A) 4.5 kmph B) 9.5 kmph C) 7.5 kmph D) 8.5 kmph E) 5.5 kmph
Speed in still water = (13 + 4)1/2 kmph = 8.5 kmph.   answer :8.5 kmph
<result>D</result>
Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes at 13 km/hr downstream and 4 km/hr upstream.