The distance between two piers on a river is miles.
It takes a motorboat, moving down river, to complete the journey.
How much time does it take the same boat to go back upstream if the current flows at ?
Explanation to correct answer:
Step-1: Speed of the motor boat.
Given,
Distance between rivers = miles
Speed of current flow of water =
Time to complete journey =
We know that
Therefore, Time to complete journey is
Let the speed of the motor boat be
When moving downriver, the net speed with which the motorboat moves is given as
Speed of the motor boat Sped of downriver
Now, we know that
Time taken
Therefore, the speed of the motorboat is
Step 2: Find the time to take the same boat to go back upstream.
When moving upstream, the net speed with which the motorboat moves is given as
Speed Speed of the motor boat Sped of downriver
Time taken
Hence, the time to take the same boat to go back upstream is .