This mathematical trick can be performed with any pack
Effect: The magician can reveal a chosen card even when it is selected with his back turned.
Method: Get a spectator to think of a number between one and 10. Then ask him to shuffle the pack (this can be be his own if you like) and get him to count down to the number thought of and make a note of the card but to leave it in the same position. Get him to do this while your back is turned.
After he has done this, turn around and take the pack placing it behind your back then rapidly count off 19 cards and as you do so reverse their order replacing them on the top of the pack. As you do this, say that you will put the card at number 20.
Finally, bring the pack from behind your back and ask the spectator which number he thought of -- for example if it was a five then begin your count with in this example 6 dealing the cards one at a time. When you reach 20, get the spectator to name his card and when you turn it over, to his amazement, it is his card.
How the Trick is Done
This is a self working mathematical trick.