In one hour, a boat goes 14 km/hr along the stream and 8 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Choose one
A) 14 km/hr  B) 13 km/hr  C) 12 km/hr  D) 11 km/hr  E) 10 km/hr
Let speed of the boat in still water = a and speed of the stream = b   Then   a + b = 14   a - b = 8   Adding these two equations, we get 2a = 22   =&gt; a = 11   ie, speed of boat in still water = 11 km/hr   ANSWER:11 km/hr
<result>D</result>
In one hour, a boat goes 14 km/hr along the stream and 8 km/hr against the stream. The speed of the boat in still water (in km/hr) is: