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 No Subject by todd)

Come to think of it, there only need to be 6 combinations of numbers to memorize if the first number of the card magician B chooses corresponds to the relative value of the first card in the line.  Eg. card 12 gives a value of "least" for the left-most audience members card.  6 combinations is a cinch to memorize. 

Posted by todd on 2007-09-18 21:27:00