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Average Speed


Date: 08/26/97 at 20:50:32
From: Patapol Pawananon
Subject: Algebra

A person travels up a hill at 10 mph. and back down at 20 mph. What is 
the average speed for the entire trip?


Date: 08/27/97 at 08:02:34
From: Doctor Anthony
Subject: Re: Algebra

The answer is NOT 15 mph because he spends longer at the slower speed.

              Let x = distance up the hill

   Time up the hill =  x/10

 Time down the hill =  x/20

         Total time =  x/10 + x/20  = 3x/20     
     Total distance = 2x

      Average speed =  2x/(3x/20)  = 40/3  =  13.333 mph

-Doctor Anthony,  The Math Forum
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