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This is an old street confidence trick, similar to the Three Card Monte, known by several different names. Darwin Ortiz detailed it in GAMBLING SCAMS; Bill Simon referred to it as The College Bet in MATHEMATICAL MAGIC; and Bob Farmer developed the Pentacle Force using this principle.
Like the Three Card Monte, this effect is frequently used as a way for a magician to demonstrate how to avoid being 'taken' on the streets.
Allow the spectator to shuffle the deck and cut it into three piles. The magician then ask the spectator to name three different cards, numerical value only. No suits are needed. Lets say the spectator picks the 2, 4, and 6. The magician now bets the spectator even money that one of those cards will appear on top of one of the three piles.
Believe it or not... the magician will win this bet 36 out of 52 times, or, about 70% of the time.
Another way this bet works is the magician allows the spectator to thoroughly shuffle the deck. The magician then names three cards and bets the spectator that if he deals three cards off the top of the deck face up on the table that at least one of the cards will be one of the cards he named.