A man can row upstream at 6km/hr and down stream at 11km/hr find mans rate in still water ?  Choose the correct choice from the following options:
A) 2.9km/hr
B) 8.5km/hr
C) 7.8km/hr
D) 85.4km/hr
E) 6.6km/hr
given upstream(u) =6km/hr   down stream (v)= 11km/hr rate in still water =1/2(u+v)=1/2(6+11)=8.5km/hr Answer is (8.5km/hr)
<result>B</result>
A man can row upstream at 6km/hr and down stream at 11km/hr find mans rate in still water ?