If 6 people meet and shake hand with each other. First person will shake hand with other 5, second person had already shaked hand with 1st person and shake hand with other 4, and so on…
So, the total no. of handshakes= 5+4+3+2+1=15 shakes
The other way to calculate this is by the formula n (n+1)/2
Where n is the no. of shake hands by very first person and that is 5.
So, the total no. of handshakes=5(5+1)/2
= 5(6)/2
=30/2
=15 shakes
