Two magicians A and B perform the following trick:

A leaves the room and B chooses 4 members from the audience at random. Each member chooses a card numbered from 1 to 100 (each chooses a different card) and after B has seen their cards he chooses a card from the remaining deck of cards. The 5 chosen cards are shuffled by an audience member and handed to A who just returned to the room. Prove that A is able to figure out which cards each member picked. Consider that the chosen members form a row and e.g. the leftmost member picks the first card and the rightmost member (B) picks the last card.

(In reply to A Little Hocus Pocus by Vernon Lewis)

"I have refrained from entering this debate because although I can perform this trick I cannot reveal the method. (It was taught to me by a Magic Circle Member with that condition)"

But maybe you can say what the method was not, and what the number of cards was.  I have shown it is impossible as stated with 100 cards.  Was a different number of cards used?  Was the method that provided by Ady Tzidon or some other method?  Perhaps it was done with chosen numbers in the abstract rather than strictly with cards, and if a large limit on the numbers' sizes, say 1000, the 5% error rate would have been deemed acceptable to magicians.  In the instances of failure they could say the "psychic vibes" weren't working, and just try again.

Posted by Charlie on 2007-05-13 12:07:23