In one hour, a boat goes 11 km/hr along the stream and 7 km/hr against the stream. The speed of the boat in still water (in km/hr) is: Choose the correct option:
A) 3 km/hr	B) 4 km/hr	C) 5 km/hr	D) 6 km/hr	E) 9 km/hr
Upstream relative speed is u + v=11km/hr   Downstream speed is u-v = 7   Where u = speed of boat in still water and v is speed of stream   Then adding two equations u+v + u-v =11+7   2u=18   Finally, u=9.   ANSW9 km/hrR : 9 km/hr
<result>E</result>
In one hour, a boat goes 11 km/hr along the stream and 7 km/hr against the stream. The speed of the boat in still water (in km/hr) is: