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?

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Answer 1 · 2016-07-03T07:25:12

7 mph.

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'.

Now,sily, (v-3)t=60=(v+3(9-t).

So, #60/(v-3)=9-60/(v+3)#.

This can be simplified to #v^2=49#, and so, v=7 mph.