The Hudson River flows at a rate o 3 mph. A patrol boat travels 60 miles upriver, and returns in a total time of 9 hours. What is the speed of the boat in still water?
Let v be the speed in still water and t hours be the time for the
journey upstream. Then, time for the journey downstream is (9-t)
hours. Use 'distance = velocity X time'.
This can be simplified to