SOLUTION: A river has a 3 mph current. A canoe travels 18 miles upstream and returns in a total of 8 hours. what is the speed of the canoe in still water?

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Question 848461: A river has a 3 mph current. A canoe travels 18 miles upstream and returns in a total of 8 hours. what is the speed of the canoe in still water?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

Let x represent the speed of the canoe in still water

18mi%2F%28x%2B3mph%29+%2B+18mi%2F%28x-3mph%29+=+8hr  |Multiplying thru by (x+3mph)(x-mph3) so as all denominators = 1

    36x = 8x^2 - 72

  8x^2 -36x - 72 = 0

  2x^2 -9x - 18 = 0

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ 

x+=+%289%2B-+sqrt%28+225%29%29%2F%284%29+ 

 x+=+%289%2B-+15%29%2F%284%29+   (Tossing out the negative solution for unit measure)

  x = 6mph is the speed of the canoe in still water

CHECKING our answer***

18mi%2F%289mph%29+%2B+18mi%2F%283mph%29 = 8hr

Wish You the Best in your Studies.