I.E. Irodov Solution problem 1.1 - A simple solution

Question 1 Physical Fundamental of Mechanics, in Problem in General Physics by I.E. Irodov.

A motor boat going downstream overcame a raft at point A, 60 mins later it turned back and passed the raft at distance of 6km from point A. Find the flow velocity of the river, assuming the duty of the motor boat to be constant.

The problem is solved using basic concepts of relative velocity and minimum calculations as possible. Here I explain the thought process involved in solving it.

[markcavendish]

I must say best solution to this problem on whole of you tube.

[AKfire]

You have used raft frame of reference. If so, then velocity of raft = 0.
How can then the raft will move 6 km in whatever time.