Question 1207696
.
What is Alicia's average speed on her walk to school if she walks 
halfway at 2 mph and runs the rest of the way at 7 mph?
~~~~~~~~~~~~~~~~~~~


<pre>
This problem is very special.


In this problem, we have two halves of the entire way,
and the halves are, of course, of equal length.


For this specific situation, the simplest way to find the average speed is to use well known formula


   average speed = {{{(2uv)/(u+v)}}} = {{{(2*2*7)/(2+7)}}} = {{{28/9}}} = 3{{{1/9}}} = 3.111111111... miles per hour.   <U>ANSWER</U>
</pre>

Solved.


This formula is specially derived and works only for the case, 
when two parts of the traveled distance have equal lengths.


-----------------


There are other ways to solve this problem.



About these other ways, &nbsp;see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/Calculating-an-average-speed.lesson>Calculating an average speed: a train going from A to B and back</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/travel/One-more-problem-on-calculating-an-average-speed.lesson>One more problem on calculating an average speed</A>  

in this site. &nbsp;&nbsp;&nbsp;&nbsp;Learn the entire subject from there.