Magic Number Cards

[bobby123]

Does anyone remember a game or magic trick probably around in the 1940s or 50s which consisted of a set of cards with many seemingly random numbers on each one. I think it may have brrn given away as a freeby in childrens comics at that time.
The trick was that the player was asked by the magican to memorise a number off one card, then asked to find the same number on another card. The magician could then tell the player what his number was by some means.
Does anyone know how this worked? What was the history of the trick? Is there a technical or mathmatical nane for this?

Cheers

[Tinker,Wales]

It's down to counting in binary.
The set of cards have one card starting with 1, one with 2, one with 4, one with 8 , 1 with 16 & 1 with 32.
So for any number up to 63, you print that number on only the cards that would show a 1 for the binary digit relating to the first numbe on the card.
e.g. 63 (binary 111111) would appear on all the cards
37 (binary 100101= 1*32, 0*16, 0*8, 1*4 0*2 1*1) would appear on the cards starting with 1,4 & 32

[TheWinner]

Hi, Yes, I remember these from my childhood. Here is a link which I searched for and found for you. I have a vague recollection that you could get small versions in a christmas cracker - David Nixon magic sets were very popular at the time

http://www.mathman.biz/html/sherimagic.html