Do Speedy Math in Your Head

Arthur Benjamin is a wizard at maths. Literally. At Hollywood's Magic Castle, the world-famous conjurer's club, he wows the crowd by multiplying big numbers — quick, what's 57,682 squared? — faster than you can use a calculator. Here he shares three cool tricks. (The answer, by the way: 3,327,213,124. See how easy it is?)

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