A man takes 3 hours 45 minutes to row a boat 20 km downstream of a river and 2 hours 30 minutes to cover a distance of 3 km upstream. Find the speed of the current.
Pick one:
A) 1 km/hr B) 2 km/hr C) 3 km/hr D) 4 km/hr E) None of these
Explanation:   First of all, we know that   speed of current = 1/2(speed downstream - speed upstream) [important]   So we need to calculate speed downstream and speed upstream first.   Speed = Distance / Time [important]   Speed upstream =(20/3 3/4)km/hr   =16/3km/hr   Speed Downstream = (3/2 1/2)km/hr   =6/5km/hr   So speed of current = 1/2(16/3−6/5)   =2km/hr   Option 2 km/hr
<result>B</result>
A man takes 3 hours 45 minutes to row a boat 20 km downstream of a river and 2 hours 30 minutes to cover a distance of 3 km upstream. Find the speed of the current.