SOLUTION: The Hudson River flows at a rate of 5 miles per hour. A patrol boat travels 40 miles upriver, and returns in a total time of 6 hours. What is the speed of the boat in still water

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: The Hudson River flows at a rate of 5 miles per hour. A patrol boat travels 40 miles upriver, and returns in a total time of 6 hours. What is the speed of the boat in still water      Log On


   

Question 180881: The Hudson River flows at a rate of 5 miles per hour. A patrol boat travels 40 miles upriver, and returns in a total time of 6 hours. What is the speed of the boat in still water?

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
The Hudson River flows at a rate of 5 miles per hour. A patrol boat travels 40 miles upriver, and returns in a total time of 6 hours. What is the speed of the boat in still water?
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x = rate of boat
40/(x-5) + 40/(x+5) = 6
Time up + time back = 6
Multiply by (x-5)*(x+5)
40(x+5) + 40(x-5) = 6(x+5)(x-5)
40x%2B200+%2B+40x-200+=+6x%5E2+-+150
80x+=+6x%5E2-150
3x%5E2+-+40x+-+75+=+0
(3x + 5)*(x - 15) = 0
x = 15
x = -5/3
Ignore the negative value
It's 15 mph