SOLUTION: The Hudson River flows at a rate of 3mph. A patrol boat travels 60 mi upriver and returns in a time of 9 hr. What is the speed of the boat in still water?

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Question 81788: The Hudson River flows at a rate of 3mph. A patrol boat travels 60 mi upriver and returns in a time of 9 hr. What is the speed of the boat in still water?
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
>
The Hudson River flows at a rate of 3mph. A patrol boat travels 60 mi 
upriver and returns in a time of 9 hr. What is the speed of the boat 
in still water?

Make this chart:

            DISTANCE   RATE     TIME
Upriver                                         
Downriver                                     

Let x be the answer.  Then since we don't have stiii water, but a river 
flowing at the rate of 3mph, so this must be subtracted for upriver speed 
and added for downriver speed.  So put in x-3 and x+3 as the two speeds 
and 60 miles for the two distances.


            DISTANCE   RATE     TIME
Upriver       60        x-3   
Downriver     60        x+3   

Now use TIME = DISTANCE/RATE to fill in the times.


            DISTANCE   RATE     TIME
Upriver       60        x-3    60%2F%28x-3%29
Downriver     60        x+3    60%2F%28x%2B3%29

Now we are told:

>>...A patrol boat travels...and returns in a time of 9 hr...<<

So the total of the times equals 9 hrs, or:

60%2F%28x-3%29 + 60%2F%28x%2B3%29 = 9

Can you solve that? You have to clear of fractions, combine
terms, and you'll have a quadratic equation that must be
solved with the quadratic formula, and when calculated gives

      x = 13.9772374 miles per hour.

Edwin