The speed of the current in a river is 6 mph. A ferry operator who works that part of the river is looking to buy a new boat for his business. Every day, his route takes him 22.5 miles against the current and back to his dock, and he needs to make this trip in a total of 9 hours. He has a boat in mind, but he can only test it on a lake where there is no current. How fast must the boat go on the lake in order for it to serve the ferry operator’s needs?

Question

anonymous · Answer

he must go 16.5 i would assume.

anonymous · Answer

how did you get to that answer?

anonymous · Answer

22.5 - 6 = 16.5

anonymous · Answer

22.5 is the usual speed and 6 is the current so take away the current on the currentless waters and you get 16.5.