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September 18, 2014

September 18, 2014

Posted by **mike** on Tuesday, September 25, 2012 at 7:47am.

- algebra -
**Reiny**, Tuesday, September 25, 2012 at 8:25amLet her rate in still water be x km/h

time in still water = 25/x hours

time to go upstream = 12/(x-2)

time to go downstream = 12/(x+2)

12/(x-2) + 12/(x+2) = 25/x

(12x + 24 + 12x - 24)/(x^2 - 4) = 25/x

24x/(x^2 - 4) = 25/x

25x^2 - 100 = 24x^2

x^2 = 100

x = ± √10

rate in still water is 10 km/h

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