Do the Twenty One Eleven Card Trick
This card trick is nice for beginners because it requires no sleight-of-hand to work -- just simple math. Even without an understanding of how the math works you can still perform this "magic" trick to impress all your friends!
Steps
- Hand your friend a stack of twenty one playing cards. Instruct them to pick one out, without showing or telling you which card they chose, and to place the card back into the stack at random.
- Deal the cards out in three columns, working row-by-row (1st column-2nd column-3rd column, 1-2-3, 1-2-3, etc). You should have three columns of seven cards in front of you. Have your friend tell you which pile contains their card (without telling you which card it is, of course).
- Gather the three columns into one stack of cards again, being sure to put the pile that holds their card in the middle of the three piles. For example if the first pile contained their card, you could pick up the third pile first, then the first pile (containing the card) and then the second pile -- or the second pile, then the first, then the third. It is very important that the pile containing their card goes into the middle.
- Repeat the past two steps two more times. When done, you will have dealt the cards out a total of 3 times.
- If you have done the card trick correctly their card will be the 11th card in the pile of cards.
- Your amazed friend may ask you how you did this. You can tell them it was magic... or you could explain the simple math that makes it work. Each time you deal out the cards you are dividing the placement of the card. By the 3rd time you have gotten the card into the middle of the pile. Thus you are able to tell where their card will be every time. The formula is Y=(X + 1)/2, where X is the number of cards and Y is the placement of the card in the pile after the 3rd deal. In this case, since X is 21, Y = 22/2 = 11.
Tips
- Here is another way of ending this trick: let your friend "find" the chosen card. Once you know the eleventh card is the correct one, you arrange all cards, face down, in four piles, 1-2-3-4, 1-2-3-4, etc. Because you have 21 cards, pile 1 will end up with six cards, and piles 2, 3, and 4 with five each. If you have followed this procedure, the correct card should be the middle card in pile 3. Now putting one hand over piles 1 and 2 and the other hand over piles 3 and 4, ask your friend: "Which do you choose, these two or these two?" Since all cards are face down, your friend has no way of knowing where the correct card is and therefore can only choose randomly. Whatever they choose, remove piles 1 and 2. (If you do this quickly, it works. If they choose 1 and 2, you simply remove what they point to; if they choose 3 and 4, you make it seem they have chosen to keep those by removing 1 and 2.) Now put one hand over pile 3 and one over pile 4 and ask them same question. Remove pile 4. Now split pile 3 into two piles, one with 3 and the other with 2 cards. (Make sure you know where the correct card has landed.) Keep doing this, removing the piles that do NOT include the correct card, until there is only one card left on the table, still face down. Ask your friend to turn it over. The fact that they "found" the correct card never ceases to amaze them.
- An alternate way to end this trick can win a bet any time. Once you have everything set up so that the eleventh card is their card, deal out 13 cards face up in a row, not a pile. Pay attention to which one is the 11th. Now say to the person, "I'll bet you the next card I flip over is yours." This wording is very important. Once they accept the bet, which they will because they KNOW the next card in the deck is NOT theirs, and they're right; you calmly grab the eleventh card you ALREADY flipped and turn it face down, so the next card you flipped was theirs.
- You can vary this trick by using a different size stack, as long as the number of cards is a multiple of 3 (3, 6, 9, 12, 15, 18, 21, 24, 27, 30, etc.). Note: if the number of cards is even, the trick is a little different: Instead of putting the pile in the middle each time, you must put the pile on the top the first time and in the middle the remaining two times. In that case the relevant equation is Y=X/2 where, again, X is the number of cards and Y is the placement of the card in the pile after the 3rd deal. With this information you can impress your friends even further by using a different number of cards each time.
Things You'll Need
- A deck of cards.
- A table or other flat surface.
- A willing friend.
