Question 992175
Greg drove to the mountains last weekend. There was heavy 
traffic on the way there, and the trip took 8 hours. When 
Greg drive home, there was no traffic and the trip only 
took 5 hours. If his average rate was 21 mph faster on 
the trip home, how far away does Greg live from the 
mountains?
<pre>
Let the answer be that Greg lives x miles from the mountains.
</pre>
>>...on the way there,...the trip took 8 hours...<<
<pre>
So his average rate going to the mountains was x miles per 
8 hours or x/8 mph.
</pre>
>>... When Greg drive home,...the trip...took 5 hours...<<
<pre>
So his average rate coming home from the mountains was x 
miles per 5 hours or x/5 mph
</pre>
>>...his average rate was 21 mph faster on the trip home...<<
<pre>
So the equation is 

                 x/5 = x/8 + 21


Solve that by multiplying through by LCD = 40

The answer is somewhere between 250 and 300 miles.

Edwin</pre>