Question 1183834
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            I will show you absolutely unexpected way to solve the problem

            (which you did not expect to see).



<pre>
For the way to school (consisting of two equal parts), you can calculate the average speed on this part 
of the traveled distance using the formula


      v = {{{(2*5*8)/(5+8)}}} = {{{80/13}}}  km/h.


Now you have two other equal parts: the way to there and the way back.


These ways are of the same length, so you can apply similar formula for the entire trip to school and back


     w = {{{(2*(80/13)*40)/(80/13+40)}}}.


I leave calculations to you.


As the answer, you should get the same number as other tutors produced in their posts.
</pre>


Regarding the formula, see my post at the link

https://www.algebra.com/algebra/homework/word/misc/Miscellaneous_Word_Problems.faq.question.1183833.html



See also 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.