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        riddles >> what happened >> Card Deck Shuffling
        
(Message started by: onlyme722 on Mar 6^th, 2008, 10:43am)

Title: Card Deck Shuffling
Post by onlyme722 on Mar 6^th, 2008, 10:43am

I don't think I'd exactly call this a riddle, but the results did get me thinking...

I take my card deck (which are the plastic, waterproof kind) and organize them in a certain way. I then proceed to shuffle once. It is a traditional bridge shuffle. I turn the cards over and find something interesting. All of the reds are on one half, all of the blacks on the other half. Most of the time when I do this, there is an average of one anomaly in each half (ie, one red mixed in at the edge of the black section and one black mixed in at the edge of the reds), but I've actually done it where it was a perfect split.

How were my cards originally organized so as to allow me to get this result after one shuffle. Keep in mind...I didn't cheat, they started out organized one way, and afterwards came out organized another way. I have actually done this, and at first I was like "I can do magic!"....but then I realized what was causing this to happen.

Title: Re: Card Deck Shuffling
Post by SMQ on Mar 6^th, 2008, 11:41am

[hide]Since a parfect riffle shuffle interleaves the old top-half of the deck with the old bottom-half of the deck, you would have started with each old half of the deck itself split in half by color. One simple way to encounter that would be if you started from a new, packaged deck which are traditionally ordered by suit in alternating colors.[/hide]

--SMQ

Title: Re: Card Deck Shuffling
Post by onlyme722 on Mar 6^th, 2008, 12:33pm

haha yupyup, I knew this wasn't a toughie, but when it first happened I was like..."hey, that's cool!"...and then I realized "well...duh".