Mathematricks: The solution
Last Friday we asked you a very tricky brain teaser:
At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?
You can test this by putting in n=1, n=2 and n=3 into the equation and checking that you get the results mentioned above
Since -12 does not correspond to a number of people at a party we take that n=11.
We need to remember that with n+1 people at a party the number of handshakes will be the sum of the first n consecutive numbers.
Therefore n+1 = 11+1 = 12. *So there were 12 people at the party. *