Mathematical explanation of the Twenty-one card trick with 27 cards: In each step, the cards are dealt into three piles. The piles are accumulated with the pile containing the target card (shaded yellow and labelled with the step number) put in the middle. After three steps, the middle card (*) is the one in all chosen piles.
The Twenty-One Card Trick, also known as the 11th card trick or three column trick, is a simple self-workingcard trick that uses basic mathematics to reveal the user's selected card.
The game uses a selection of 21 cards out of a standard deck. These are shuffled and the player selects one at random. The cards are then dealt out face up in three columns of 7 cards each. The player points to the column containing their card. The cards are picked up and the process is repeated three times, at which point the magician reveals the selected card.
Variations
Minor aspects of the presentation are adjustable, for example the cards can be dealt either face-up or face-down. If they are dealt face-down then the spectator must look through each of the piles until finding which one contains the selected card, whereas if they are dealt face-up then an attentive spectator can immediately answer the question of which pile contains the selected card. Some performers deal the cards into face-up rows or columns instead of piles, which saves more time as all cards are partly visible.
When the same method is applied to three piles of nine cards each, it is called the 27 card trick. It is identical in principle.
Method
The magician begins by handing the spectator the 21-card packet and asking them to look through it and select any one card to remember.
The cards are then dealt into three piles one at a time, like when dealing out hands in a card game. Each time they are dealt out, after the spectator indicates which pile contains the thought-of card, the magician places that pile between the other two. After the first time, the card will be one of the ones in position 8-14.
Animation demonstrating how the method excludes incorrect cards each time a pile is selected, leaving the selected card in position 11.
When the cards are dealt out the second time, the selection will be the third, fourth, or fifth card in the pile it ends up in. In picking up the piles, the magician places this pile between the other two again. This ensures that the selection will now be one of the ones in position 10-12.
The third time the cards are dealt out, the selection will be the fourth card in whichever pile it ends up in. On the third deal, as soon as the spectator indicates which pile contains the selection, the magician knows that it is the fourth, or middle, card in that pile. If the magician gathers up the piles again, as before with the pile containing the selection in the middle, the selection will be the eleventh card in the 21 card packet.
If 27 cards are used, the procedure is the same but the selection will be the fourteenth card in the packet.
Shuffling is a procedure used to randomize a deck of playing cards to provide an element of chance in card games. Shuffling is often followed by a cut, to help ensure that the shuffler has not manipulated the outcome.
Klondike is a card game for one player and the best known and most popular version of the patience or solitaire family, as well as one of the most challenging in widespread play. It has spawned numerous variants including Batsford, Easthaven, King Albert, Thumb and Pouch, Somerset or Usk and Whitehead, as well as the American variants of the games, Agnes and Westcliff. The distinguishing feature of all variants is a triangular layout of the tableau, building in ascending sequence and packing in descending order.
Spit is a card game of the shedding family for two players. It is a form of competitive patience. The game is played until all of a player's cards are gone. It has a close variant known as Speed. Spit appears to have originated in the UK in the 1980s.
A trick deck is a deck of playing cards that has been altered in some way to allow magicians to perform certain card tricks where sleight of hand would be too difficult or impractical.
Perpetual Motion is a Patience game which has the objective of discarding playing cards from the tableau. The name relates to the time-consuming process of the game. It is also called Idiot's Delight or Narcotic.
Gargantua is a patience or solitaire card game that is a version of Klondike using two decks. It is also known as Double Klondike.
Canfield (US) or Demon (UK) is a patience or solitaire card game with a very low probability of winning. It is an English game first called Demon Patience and described as "the best game for one pack that has yet been invented". It was popularised in the United States in the early 20th century as a result of a story that casino owner Richard A. Canfield had turned it into a gambling game, although it may actually have been Klondike and not Demon that was played at his casino. As a result, it became known as Canfield in the United States, while continuing to be called Demon Patience in the United Kingdom and elsewhere. It is closely related to Klondike, and is one of the most popular games of its type.
Out of This World is a card trick created by magician Paul Curry in 1942, in which an audience member is asked to sort a deck into piles of red and black cards, without looking at the faces. Many performers have devised their own variations of this trick. It is often billed as "the trick that fooled Winston Churchill" due to a story describing how it was performed for him during World War II. The method behind the trick is simple and essentially self-working, and can be enhanced by the presentation of the performer and the use of other principles of magic.
British Square is a patience or solitaire card game which uses two decks of 52 playing cards each. It is a fan-type game in the style of La Belle Lucie. It has an unusual feature of switchback building whereby each foundation is first built up and then built down.
Crescent is a solitaire card game played with two decks of playing cards mixed together. The game is so called because when the cards are dealt properly, the resulting piles should form a large arc or a crescent. An alternative and less common name for the game is La Demi-Lune.
Speed is a game for two players of the shedding family of card games, in which players try to get rid of all of their cards first. It is a form of competitive patience similar to Spit.
Capricieuse is an old English patience played using two packs of playing cards. Some authors call it Capricious.
Westcliff is the name of two closely related patience or card solitaire games of the simple packer type, both of which are played using a deck of 52 playing cards. One version is particularly easy to win, with odds of 9 in 10; the other is harder with odds closer to 1 in 4. The game has a variant, Easthaven.
This is a glossary of conjuring terms used by magicians.
Emperor is an English patience or solitaire card game which is played using two packs of playing cards. Although similar to other members of the large Napoleon at St Helena family, Emperor introduced the unique and distinguishing feature of worrying back as well as the novel term "sealed packet".
Spelling Bee may refer to one of several card tricks that revolve around the spelling of card types, audience member names, or words suggested by the audience. Many make use of decks prepared in advance in order to provide the illusion of spelling card names in a particular sequence. Jean Hugard's Encyclopedia of Card Tricks lists a number of such spelling-based tricks, many of which are considered to be self-working.
Seven Devils is a solitaire game in the style of Canfield played with two decks of playing cards. It is considered to be a very difficult solitaire game.
Duchess of Luynes is a patience or card solitaire game played with two packs of playing cards. It is a member of the Sir Tommy family. A unique feature of this game is the building of the reserve, which is not used until the entire stock runs out.
Travellers is a card game of the patience or card solitaire genre which uses a single card pack of either 52 or 32 playing cards. It is an interesting game based on "an entirely new principle" which Parlett describes as a "rhythmical feature that might be called 'shuttling'", as in the game of Weavers. It should not be confused with the twin-pack patience game, also called Travellers.
Kratzen is an Austrian card game for three to six players that is played for small stakes usually using a 33-card William Tell pack. It is a member of the Rams group of card games characterised by allowing players to drop out of the current game if they think they will be unable to win any tricks or a minimum number of tricks. The game is related to the Swiss Jass form, Chratze and has been described as "fun" to play.
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