A man takes 10 hours to row 21 km upstream from point A to point B and back to A by boat. If he takes the same time to row 7 km downstream as upstream. If it takes time to cover 3 kilometers then find the velocity of the stream and the speed of the boat in still water.
Let the speed of boat in still water =B and speed of stream =S then Speed of boat in downstream=B+S and distance =7km So now -time =7/B+S Speed of boat upstream =B-S and Distance =3km So, time = 3/B-S ATQ- 3/(B-S)=7/(B+S) 7B-7S=3B+3S 4B=10S B =5S/2 
And Speed of boat in still water = B =5km/h
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