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December 20, 2014

December 20, 2014

Posted by **Anonymous** on Monday, March 25, 2013 at 7:58pm.

- math -
**Reiny**, Monday, March 25, 2013 at 8:54pmtime to go up hill = d/10

time to go down = d/30

total time = d/10 + d/30 = 4d/30

avg speed = total distance / total time

= 2d/(4d/30)

= 2d(30/4d)

= 60/4 = 15 mph

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