So get someone to write down four numbers. When he/she adds them up, You've already got them written down.
First, you multiply the year by two. For example: Year: 2010 Final Number: 4020. Once you get this number, write it down! This is the number the volunteer will have written down on their piece of paper.
Give the volunteer the other piece of paper. Tell him/her to write down the year he/she was born. Next tell the person to write down the year he/she had a special event accure in their life. Then, tell them to write down their age. Finally, tell them to write down the number of years that have past since the year of the special event.
Tell the volunteer to add these numbers together. This should turn out to be the number that you wrote down.
Show the number you wrote down to the volunteer. WOW! It's the number that they got! AMAZING!