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January 28, 2015

January 28, 2015

Posted by **Cerra** on Saturday, November 27, 2010 at 5:41pm.

- math -
**Reiny**, Saturday, November 27, 2010 at 7:02pmrate of faster person = 1/x

rate of slower person = 1/(x+1)

combined rate = 1/x + 1/(x+1) = (2x+1)/(x(x+1))

so time with combined rate = 1/[(2x+1)/(x(x+1))

= x(x+1)/(2x+1)

so x(x+1)/(2x+1) = 4

x^2 + x = 8x + 4

x^2 - 7x -4 = 0

x = (7 ± √ 65)/2

= 7.53 or a negatiave

So one takes 7.53 hours, the other 8.53 hours

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