Question 1152008
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            Standard (but not unique (!) ) solution to this problem is as follows.



<pre>
Each person makes  (n-1) handshakes, so your first intention is to answer n*(n-1) handshakes, in all.


But be careful (!)


By counting in this way, we count each handshake twice, for every of the two hand shakers. 


Therefore, we must divide  n*(n-1)  by 2, and then we come to the correct answer:


    the number of handshakes is  {{{(n*(n-1))/2}}}.    <U>ANSWER</U>
</pre>

Solved.


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It is classic problem (!)


MEMORIZE its solution (!)