SOLUTION: Bill paddled a canoe 2 miles upstream in a river that has a current of 2 mph. He then turned around and paddled downstream until he reached his original starting place. If the enti

Question 679495: Bill paddled a canoe 2 miles upstream in a river that has a current of 2 mph. He then turned around and paddled downstream until he reached his original starting place. If the entire trip took him 7 hours, how fast would Bill paddle in still water?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Bill paddled a canoe 2 miles upstream in a river that has a current of 2 mph. He then turned around and paddled downstream until he reached his original starting place. If the entire trip took him 7 hours, how fast would Bill paddle in still water?
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Let his still-water rate be "r":
Let his distance be "x" for each leg of the journey:
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Equation:
time + time = 7 hrs
2/(r+2)+2/(r-2) = 7
2(r-2) + 2(r+2) = 7(r^2-4)
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4r = 7r^2 - 28
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7r^2 - 4r - 28 = 0
Positive solution using Quadratic formula:
r = 2.306.. mph
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Cheers,
Stan H.
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