Find the number of heads from hands!!

Posted: October 4, 2012 in Br@!n Te@$er$, M@th puzzles


There was a friends get together event, after a long time. And everyone shake hands with every friend.

If there was total #66 handshakes, find the number of friends met up that evening.

Have a good day!



  1. Sriya says:

    answer is 12.
    consider n people. making
    n*(n-1) handshakes. however each handshake is considered twice in this case so n*(n-1)/2.

    n=12 or n=-11
    So the answer is 12!

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