When it comes to randomizing a deck of cards, mathematicians have finally found the magic number of shuffling needed.
The answer? Seven.
First of all, let’s clear the fact that we are talking about the riffle shuffle here. Riffle shuffle is the one that you divide the deck in half, holding a half in each hand with the thumbs inward and then releasing the cards one by one so the two parts are mixed together (the one in the picture above). Here’s the story. (the article continues after the ad)
In 1992, mathematicians Bayer and Diaconis showed that after a total of seven riffle shuffles, a deck of cards is fully randomized. This means that every configuration is equally likely. Shuffling more than 7 times does not makes much of a difference in the deck’s randomness. If you shuffle less though, you will end up with a deck that’s far from random.
Speaking of shuffling, the other known method, the overhand shuffle, is not effective at all: it takes nearly 10,00 overhand shuffles to randomize a deck of 52 cards!
If you like what you read, then you will definitely love this one: Which Is The Best Way To Shuffle A Deck Of Cards?
Photo: Poker Photos / Flickr