If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 6 kmph, then the speed of the boat in still water is :	Choose the correct choice from the following options
A) 2.5 km/hr  B) 4 km/hr  C) 5 km/hr  D) 10.5 km/hr  E) None of these
Solution   Speed of stream = 1/2 (16-8) km/hr= 4kmph . Answer 4 km/hr
<result>B</result>
If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 6 kmph, then the speed of the boat in still water is :