This is a magic trick performed by two magicians, A and B, with one regular, shuffled deck of 52 cards. A asks a member of the audience to randomly select 5 cards out of a deck. the audience member -- who we will refer to as C from here on -- then hands the 5 cards back to magician A. After looking at the 5 cards, A picks one of the 5 cards and gives it back to C. A then arranges the other four cards in some way, and gives those 4 cards face down, in a neat pile, to B. B looks at these 4 cards and then determines what card is in C's hand (the missing 5th card). How is this trick done?

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Note 1: There's no secretive message communication in the solution, like encoded speech or ninja hand signals or ESP or whatever ... the only communication between the two magicians is in the logic of the 4 cards transferred from A to B. Think of these magicians as mathematicians.

Note 2: This magic trick is originally credited to magician and mathematician Fitch Cheney.

(In reply to This is not the solution but close by Charlie)

This is basically the same idea I had.

The last bit of information can be in whether the cards are placed down upright (portrait) or sideways (landscape.)

The actual encoding of the 5th card into these four seems likely to be a mentally straining process but one that could be mastered with effort. 

Posted by Jer on 2009-05-29 13:51:34