Question 1208236
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David jogged for 5 days in a row. Each day he jogged 1.4km more than the day before. 
At the end of 5 days he jogged a total of 20.6km. How far did he jogged on the 5th day.
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            Consider this simple way solving.



<pre>
The average distance, which David jogged per day, is  {{{20.6/5}}} = 4.12 kilometers.


Intuitively, it is clear that this average distance is the distance which David jogged on the 3rd day

(3rd term is the central term of an arithmetic sequence of 5 terms).


From here, we conclude that on the 4th day David jogged 4.12 + 1.4 = 5.52 kilometers,

                            on the 5th day David jogged 5.52 + 1.4 = 6.92 kilometers.    <U>ANSWER</U>
</pre>

Solved mentally without using any equations.



To me, the entire educational meaning of this problem for a student is to find  a straightforward 
simplest way to solve to the end, avoiding long boring calculations and long boring reasoning.


One brilliant idea dissects the problem and solves it instantly.