In one hour, a boat goes 6 km/hr along the stream and 2 km/hr against the stream. The speed of the boat in still water (in km/hr) is:	Choose the correct choice from the following options:
A) 3 km/hr
B) 4 km/hr
C) 5 km/hr
D) 6 km/hr
E) 8 km/hr
Upstream relative speed is u + v=6km/hr   Downstream speed is u-v = 2   Where u = speed of boat in still water and v is speed of stream   Then adding two equations u+v + u-v =6+2   2u=8   Finally, u=4.   ANSWER : 4 km/hr
<result>B</result>
In one hour, a boat goes 6 km/hr along the stream and 2 km/hr against the stream. The speed of the boat in still water (in km/hr) is: