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 the magician A coaches partner B by Ady TZIDON)

Glad you liked it :) This puzzle is from Finnish highschool math competition but I have no idea wether or not this has been actually ever performed or what the original source is. This trick isn't that "impossible" so I guess with a little practice some clever persons could actually pull this off. We usually have lame problems in combinatory and I found this one very interesting

Posted by atheron on 2007-05-12 14:38:33