A boatman rows 96 km downstream in 8 hours with a stream speed of 4kmph. How much time will he take to cover 8km upstream?
Answer: C
Speed = distance/time
Speed downstream: 96 / 8 km/hr = 12kmph
Speed of stream = 4kmph
Effective speed of boat = (12-4) kmph
= 8kmph
Distance to be travelled upstream= 8 km
Speed upstream = boat speed-current speed
= 8-4 kmph
= 4 kmph
Time taken = distance/speed = 8/ 4 hours
=2 hours
Thus it will take 2 hours to go upstream.