SOLUTION: felix rode 18 miles downstrem and back to the same place where he started, in 3 hours and 12 minutes. find the rate of felix in still water if the velocity of the stream is 3 miles

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Question 759443: felix rode 18 miles downstrem and back to the same place where he started, in 3 hours and 12 minutes. find the rate of felix in still water if the velocity of the stream is 3 miles per hour
Answer by lwsshak3(11628) About Me  (Show Source):
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felix rode 18 miles downstrem and back to the same place where he started, in 3 hours and 12 minutes. find the rate of felix in still water if the velocity of the stream is 3 miles per hour.
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let x=rate of Felix in still water
x+3=rate downstream
x-3=rate upstream
travel time=distance/rate
3hr and 12 min=16/5 hrs
18%2F%28x%2B3%29%2B18%2F%28x-3%29=16%2F5
LCD:5(x+3)(x-3)
5%2A18%2A%28x-3%29%2B5%2A18%2A%28x%2B3%29=16%28x-3%29%28x%2B3%29
90x-270%2B90x%2B270=16x%5E2-144
16x^2-180x-144=0
4x^2-45x-36=0
(4x+3)(x-12)=0
x=-3/4 (reject, x>0)
or
x=12
rate of Felix in still water=12 mph