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March 5, 2015

March 5, 2015

Posted by **jim** on Monday, August 16, 2010 at 10:18pm.

- algebra -
**drwls**, Monday, August 16, 2010 at 10:31pmCall the initial speed V (in miles/h) and the time driving at that speed be t (in hours).

V*t + (V+15)*(1-t) = 50

V*t = 30

30 + (V+15)(1 - 30/V) = 50

(V+15)(1 - 30/V) = 20

V + 15 -30 -450/V = 20

V - 450/V = 35

V^2 -35V -450 = 0

(V-45)(V+10) = 0

Only the positive root, V = 45 mph, makes sense. Rachel finishes the trip at 60 mph

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