Math and Magic

Begin the course with card tricks in which mathematics is clearly being used, but the secret is not easy to figure out. Learn the invariant principle: Some qualities stay the same in a deck even though the order of cards is changing. End with what Professor Benjamin calls the tear-able" trick, being careful to use cards that you don't mind wrecking."

Explore card tricks in which the cards are shuffled, dealt, and flipped over in interesting ways, leading to surprising outcomes. Discover Hummer's principle-an endless source of mystifying, crowd-pleasing tricks, based on random mixing of cards combined with a simple procedure that preserves a pattern that seems positively magical.

Professor Benjamin shows how to play cards like someone who would be thrown out of a casino. Learn the Jonah principle for always winning at poker. Get a feel" for counting cards and develop the knack for telepathically communicating a hidden card to an assistant. Finally, who could claim to be a card shark without a trick that turns up four aces every time?"

Investigate tricks based on the cyclic method of card ordering, or stacking," popularized by magician Si Stebbins and tracing originally to one of the first books on magic, published in Italy in 1593. Learn how to seemingly weigh a deck of cards in your hands and other miraculous feats based on this simple principle."

Professor Benjamin introduces a special guest, mathematician and magician Brent Morris, master of the perfect shuffle (also known as the faro shuffle), in which two equal halves of the deck are interlaced perfectly. You will learn two versions of this virtuoso technique-the in-shuffle and out-shuffle-along with sequences of shuffles that lead to very interesting symmetries.

Explore results of an ordinary riffle shuffle, where the deck is cut roughly in half, and the cards are interlaced approximately-but usually not perfectly. Depending on how the cards are arranged beforehand, intriguing effects are possible, based on Gilbreath's principle of patterned sequences. Study several of these magic showpieces.

Master an impressive medley of number-guessing tricks, involving the golden ratio, the Fibonacci series, and other notable numbers. In analyzing how the tricks work, discover how straightforward algebraic expressions are secretly pulling the strings. The feats include the very first mathematical magic trick that Professor Benjamin learned.

You don't have to be a genius to look like one. Drawing on young volunteers, Professor Benjamin shows easy strategies for mentally multiplying numbers by 11, dividing numbers by 91, multiplying any numbers near 100, squaring numbers ending in 5, and other seemingly fearless feats of arithmetic, without use of a calculator.

Admire the magic of the number nine. An ancient technique called "casting out nines" lets you pick out the missing digit in a bewilderingly long series of operations. Then learn to determine two-digit cube roots and also find the age of a volunteer who has hidden the number in a complicated calculation-all with the help of the number nine.

Hone your psychic powers by developing tricks such as these: Have someone scramble their birthday in a seemingly unbreakable code, which you decipher with ease. Calculate the hidden spots on a stack of dice. Use the parity principle to guess where your partner has landed in an alphabetic array. Also learn the magician's toxic" calculation principle."

Explore mathematical mysteries that seem geometrically or topologically odd. Consider a paper strip with a half twist, joined end-to-end, known as a Mobius band. What happens when there are more twists or if the shape is cut? Create an analogous shape by slicing a bagel. Also, solve puzzles with disappearing figures, including a rabbit.

Since ancient times, magic squares have given endless hours of fun through designing grids of numbers where each row, column, and diagonal produces the same sum-as if by magic. In this last lesson, learn to create magic squares quickly from numbers provided by your amazed audience or based on your volunteer's birthday. Finally, end the course with a magic matrix based on the number pi