In one hour, a boat goes 15 km/hr along the stream and 9 km/hr against the stream. The speed of the boat in still water (in km/hr) is:  Choose the most appropriate option:  A) 12 kmph  B) 13 kmph  C) 14 kmph  D) 15 kmph  E) 16 kmph
Explanation:   Let the speed downstream be a km/hr and the speed upstream be b km/hr, then   Speed in still water =1/2(a+b) km/hr   Rate of stream = 1/2(a−b) km/hr   Speed in still water = 1/2(15+9) kmph = 12 kmph.   12 kmphnswer: Option 12 kmph
<result>A</result>
In one hour, a boat goes 15 km/hr along the stream and 9 km/hr against the stream. The speed of the boat in still water (in km/hr) is: