Question 1192365
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    {{{(20*(20-1))/2}}} = {{{(20*19)/2}}} = 10*190 = 190 handshakes.     <U>ANSWER</U>


Each person makes 20-1= 19 handshakes with other 19 persons.


But since the product 20*19 counts each single handshake twice, we divide this product by 2, getting the correct answer.
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Solved and explained.