Explanation
To solve this efficiently, we can use the concept of Relative Motion with respect to the flowing river.
1. Relative Speed Approach:
Let the speed of the boat in still water be v and the speed of the river current be u.
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When the boat moves with respect to the river (water), its speed is always v, whether it goes downstream or upstream.
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The raft is floating freely, so its speed with respect to the water is zero.
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Since the boat takes 1 hour to move away from the raft (downstream), it must take exactly the same amount of time (1 hour) to return to the raft (upstream) relative to the water.
2. Total Time Calculation:
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Time taken to move away from point A: T1=1 hour.
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Time taken to return to the raft: T2=1 hour.
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Total time the raft has been drifting: Ttotal=T1+T2=2 hours.
3. Finding the River Speed (u):
The raft traveled from point A to point B in this total time.
