I have seen a number of people twittering and talking and whatever about this for them magic:
If you take the last two digits of the year you are born and then add your age you will get the number 111.
Here is first an example:
I am born in 1965, and the last two digits is then 65. I am this year turning 46, and 65+46=111.
The reason for this is as follows:
Lets say you are born on year Y.
The two last digits of the year you are born is (Y-1900).
Your age is (2011-Y).
If you add these two numbers you get (2011-Y) + (Y-1900).
This is the same as (2011-Y+Y-1900).
Which in turn is the same as (2011-1900).
Which is 111.
Updated: A friend of mine points out that if the person is born year 2000 or later, then my “proof” is not correct. Indeed, the magic number is then 11:
(Y-2000) is then the last two digits, so instead we have (2011-Y)+(Y-2000) which is (2011-2000) which is 11.