Here’s a self-working card trick my dad showed me when I was but a wee lad. It sounds pretty uninteresting in the telling, but try it out–in practice, people are amazed at the outcome.
- Take a standard, 52 card deck and randomly discard ten cards. I prefer to do this before the trick starts and never tell the audience, but you can do it in the middle (step 6) if you’re feeling honest. These ten cards will play no part in the trick.
- Deal the 42 cards into piles using the following method: Flip the top card from your deck face up, announce the value aloud (e.g., “seven!”) and place it on the table as a foundation of a pile. Now continue to deal cards onto that pile, counting upwards with each card, until you hit thirteen. So after putting the 7 card face up, for instance, you would deal five cards onto it, counting “Eight”, “Nine,” “Ten,” “Jack,” “Queen,” “King!”. If the foundation card is an Ace you will create a 13-card pile; if it is a King it will constitute a pile unto itself. When a pile is complete, turn it face down and start a new pile with the next card. If the final cards in the deck do not make a complete pile (e.g., you flip over a “Three” but only have five cards remaining) set them aside for the moment.
- Ask your audience to pick three of the face-down piles. Take all the unchosen piles, combine them with the remainders from step 2 (if any), and hand the deck to your audience.
- Tell your audience to flip over the top card on one of the three, face-down piles. After he has done so, tell him to discard that many cards from his deck. So if he flipped over a 9, he would discard nine cards from his deck.
- Tell your audience to flip over the top card on a second pile and, again, discard that many cards.
- Only if you did not remove cards in step 1: tell your audience to discard ten more cards “for good measure”.
- Tell your audience to count how many cards he has left in his hand. Then tell him to flip over the top card on the last of the three face-down piles. If you’ve done everything correctly, the value of the card will equal the number of cards he holds.
The best thing about this “trick,” I’ve found, is that there’s is no trick–it’s just math–so you can feel free to reveal the secret when you’re done (where “secret” = “just take out 10 cards before you start and do what I did.”). This is especially good for kids because, requiring no sleight of hand or misdirection, it is virtually un-screw-up-able, so long as they follow the recipe.
If, on the other hand, someone is dismissive because it is “just a formula,” hand him all 52 cards and challenge him to recreate the trick. Assuming they don’t know to take out 10 cards ahead of time, their attempt will end in gloatworthy failure.