# A cool mathematical card trick thing based on 13

Somebody showed this to me years ago. I just revisited it and worked out the math to get it right. I’m now logging for permanent reference, as the details can be easily forgotten with time.

Start with a normal jokerless deck of 52 cards. Consider each card as being numbered 1 through 13, with Aces being 1, Jacks being 11, Queens being 12, and Kings being 13.

1. Turn the first card face up. Declare the value of the card, and then continue to turn cards one at a time on top of it, counting up to 13. For instance, if the first turned card is, say, 7 of Diamonds, you declare “Seven,” and continue turning cards up while counting “…eight, nine, ten, eleven, twelve, thirteen.”

2. Continue this process, making new stacks each time. When you’re done, you should have four or more separate stacks of cards, face up. You’ll likely have a few surplus cards in your hand, which you hold for the time being.

3. Turn all of the stacks face down.

4. Have a friend point to three of the stacks. Leave those three stacks where they are, and take the remaining stacks into your hand, holding them face down in your palm.

5. From the cards in your hand, deal ten cards face down into their own discard pile, counting out loud as you do so. “One, two, three, four, five, six, seven, eight, nine, ten.”

6. Have a friend turn the top card over on one of the three stacks. Take the value of the card, and count cards from your palm into your discard pile. For instance, if your friend turned a 6 of Spades, count down six cards face down into your discard pile, declaring out loud, “One, two, three, four, five, six.”

7. Have your friend turn the top card over on another one of the stacks. That is, if it’s, say, a Jack of Hearts, count down eleven cards from your hand. “One, two, three, four, five, six, seven, eight, nine, ten, eleven.”

You now have X amount of cards left in your hand, and one remaining stack down in front of your friend.

8. Deal the remaining cards you have in your hand into the discard pile, counting out loud. Say you have four cards left. “One, two, three, four.”

9. Have your friend turn the top card off that third stack.

Cool, right?

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