arithmetic - a man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2 hours 30 minutes to cover a distance of 5 km upstream find the speed of the current - skillgun

Speed of current = 1/2(speed downstream - speed upstream)
So we need to calculate speed downstream and speed upstream first.
Speed = Distance / Time [important]
Speed upstream =(15334)km/hr=15×415 = 4 km/hr
Speed Downstream = (5212)km/hr=5×25 = 2 km/hr
So speed of current = 12(4-2) =1 km/hr