October 2018 - Math Problem

If there were 8 people at a party and everyone shook everyone else's hand exactly once, how many handshakes would there be in total?

Solution:

​Number of People Who Have Arrived  ​Number of Handshakes
​0 ​0
​2 ​1
​3 3​
​4 6​
​5 10​
​6 15​
​7 ​21
​8 ​28


How many handshakes would there be if there were 10 people? What about 100 people?
 

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