Question

a Boat can cover 10 kilometre upstream and 5 km downstream in 6 hours if the speed of the stream is 1.5 kilometre per hour find the speed of the boat in still water

Answer 1

in still water we neglect the speed of the stream and deal with the other information
speed=distance/time
speed=10+5/6
speed=15/6
speed=2.5km/h