This card number is simple because no sleight of hand is needed, but pure and simple math. Even without understanding how math works, you can still perform this "magic" trick to impress all your friends!
Steps
Method 1 of 2: Eleventh Card
Step 1. Hand your friend a deck of 21 cards
Tell him to pick and pull one out, without showing it to you or telling you which card he chose, and put it back in the deck at random.
Step 2. Distribute the cards face up in three columns, going row by row (first column, second column, third column, 1-2-3, 1-2-3, etc.)
You should have three columns of seven cards in front of you. Get your friend to tell you which pile his card is in (without telling you which card is, of course).
Step 3. Gather the three columns back into one deck
This time, be careful to put the column in which the card is in the middle of the other two columns. For example, if the card is in the first column, you can pick up the third first, then the first (the one with the card) and then the second - or the second, then the first, then the third. It is very important that the column with the card is in the middle of the other two.
Step 4. Repeat the last two steps two more times
Eventually, you will have dealt the cards 3 times in all. If you have done the number correctly, the card will be the eleventh in the deck. Don't turn the deck upside down at the end, or you won't hit the jackpot.
Method 2 of 2: Red and Black
Step 1. From a deck of 52, divide the cards into two equal piles of 26 each
It would be a complete deck "without" the jokers. Perhaps you should first check the deck to make sure that the cards are all and there are no duplicates.
Step 2. Give one of these decks to the spectator and keep the other
If he wants more control, let him choose the deck he prefers.
Step 3. Explain to him that you will make the number of red cards in your deck equal to the number of black cards in his
The math behind it is pretty simple, but most people won't be thinking about the trick or trying to figure it out.
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The trick is that when you build 26 cards, there will ALWAYS be one with the same number of red cards as the other black cards. For example, if there are 10 red cards in your deck of 26 cards, the remaining 16 are necessarily black. Therefore, the spectator's pack of 26 cards MUST contain the remaining 16 red cards (compared to your 10 reds) and the remaining 10 black cards (compared to your 16 blacks). So, as you can see, the number of red cards in your deck (10) equals the number of black cards (10) in the spectator's deck.
And, of course, the opposite is true: the number of black cards (16) in your deck equals the number of red cards (16) in the spectator's deck. Stack A is always the same as stack B at the level of red and black cards
Step 4. Make the number more interesting by staging it however you like
This way you make it more of a show and the viewer is more involved and intrigued, not knowing how you do it. Make it interesting and fun by being the first to be dynamic and engaging.
You can make variations by creating three bunches, so you add another dimension to the overall effect and create a diversion. Then you will say that the number of red cards in your two piles equals the number of black cards in the deck chosen by the spectator
Step 5. Charm them with your magic number
Let the spectator uncover the cards and then, slowly and dramatically, uncover yours. Wave your hands a little, indicating the magical air you cast on the deck. How did you do? Never reveal it.
