What is a Perfect Shuffle?
Here's how it works...
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Imagine a pile of cards labeled 1 through 20 and piled in order. Now, divide the pile exactly in half. The cards are shuffled by alternately taking a card from each pile.
Note this is not random. That is why it is called a perfect shuffle. It is possible to track the movement of each card as they are shuffled. (Actually this is called a in-shuffle. The shuffle was started with the bottom pile of cards causing cards 1 and 20 at the edges of the pile to move in towards the center. It is also possible to do a out-shuffle by starting the shuffle with the top pile of cards. This causes cards 1 and 20 to stay out on the edges. My scarves use only in-shuffles. To learn more about in and out shuffles and how it is possible to use a combination of them to move a card to any place in a deck check out some of the links on my find out more page.) |
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If the perfect shuffle is repeated enough times the cards will return to their original order. The number of shuffles that this takes depends on the number of cards used. See the what's going on with the math page to learn more. For this example of 20 cards it takes 6 perfect shuffles for the cards to return.
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Notice that groups of cards travel around together. In this example the cards 1, 2, 4, 8, 11, & 16 all trade places with only each other. If each group is given a color, this pattern can be represented visually.
I used this method with various numbers of cards to created the patters of strips in the scarves I knit. Now you're ready to see more perfect shuffle scarves I've made. |
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What's going on with the math?
Knit your own perfect shuffle scarf.
Who came up with this brilliant idea?
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