In one hour, a boat goes 21 km/hr along the stream and 11 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Choose the correct choice from the following
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(21+11) kmph = 16 kmph.   Answer: Option 16 kmph
<result>E</result>
In one hour, a boat goes 21 km/hr along the stream and 11 km/hr against the stream. The speed of the boat in still water (in km/hr) is: