<PRE><B>Question 1010003</B>
Stephanie took her kayak to the kaweak river, which flows downstream at a rate of 2 kilometers per hours. She paddled 15 km upstream, and then paddle downstream to her starting point. If this round trip took a total of 4 hours, find the speed that Stephanie can paddle in still water. 
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Upstream DATA::
distance = 15 km ; rate = b-2 mph ; time = 15/(b-2) hrs
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Downstream DATA:
distance = 15 km ; rate = b+2 mph ; time = 15/(b+2) hrs
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Equation:
time + time = 4 hrs
15/(b-2) + 15/(b+2) = 4
15(b+2) + 15(b-2) = 4(b^2-4)
30b = 4b^2 - 16
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2b^2 - 15b - 8 = 0
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Factor::
2b^2 - 16b+ b - 8 = 0
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2b(b-8) + b-8 = 0
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(b-8)(2b+1) = 0
Positive solution::
boat speed = 8 km/hr
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Cheers,
Stan H.
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