Your thinking of...
http://www.themagicteacher.com/articles/801/1/Your-thinking-of/Page1.html
Leon Frerry
I'm in the middle of creating a magic trick called 'Stealth'
It's a coin vanish and it's very clean By Leon Frerry
Published on 08/12/2008
Effect: You tell your spectator to pick a number and do some math... You then name the number that they are now thinking of...
THE TRICK!!!
Effect: You tell your spectator to pick a number and do some math... You then name the number that they are now thinking of...
Secret: Tell them pick a number between 1 and 100, tell them multiply it by 2, add 8 to it, divide it by 2 and subtract the original number, IT SHOULD BE 4!!!! Now, pretend to concentrate and then name their number to be 4
Works about 99% of the time