In one hour, a boat goes 4 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 option:
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=4km/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 =4+2   2u=6   Finally, u=3.   3 km/hrNSWER : 3 km/hr
<result>A</result>
In one hour, a boat goes 4 km/hr along the stream and 2 km/hr against the stream. The speed of the boat in still water (in km/hr) is: