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In a classroom, there is 31 people. If everyone shakes everyone else's hand once, then how many total handshakes happened?

 Jul 6, 2020
 #1
avatar+643 
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The formula for number of handshakes is n(n-1)/2 where n is the number of people. Plug 31 for n into the equation.

 

n(n-1)/2

=31(31-1)/2

=31(30)/2

= 465 handshakes

 Jul 6, 2020
 #2
avatar+26007 
+1

31 people have to shake hands with 30 other people 

31 * 30 = 930     BUT each handshake involves TWO people , so divide that number by 2    = 465 handshakes  ( as gs found below)

 Jul 6, 2020

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