If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 5 kmph, then the speed of the boat in still water is :	Choose the correct choice from the following answers:  A) 3.5 km/hr  B) 4.2 km/hr  C) 5 km/hr  D) 10.5 km/hr  E) None of these
Solution   Speed of stream = 1/2 (15-8) km/hr= 3.5kmph . 3.5 km/hrnswer 3.5 km/hr
<result>A</result>
If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 5 kmph, then the speed of the boat in still water is :