Kozar Prediction Notepad

The magician introduces a sealed envelope, which contains a prediction (in fact, this can be mailed to the organizers of your show weeks in advance!). Three spectators are then asked to write 3 numbers between 100 and 999 on a note pad. The pad is then handed to a fourth spectator, who adds the numbers. When the total is announced, the envelope is opened, showing your prediction to match! Remember - the spectators handle the note pad themselves, and you never touch the envelope!