"Some of the ancient methods of calculation are particularly suited to mental arithmetic. ...Multiplication by a power of two is easily performed by successive doubling—a method fundamental to Egyptian multiplication (and division). Many 'tricks'... have been known for centuries. ...think of multiplication by a number close to a power of 10. How many children have been asked laboriously to multiply by 97 instead of multiplying by 100, [multiplying the original number again] by 3, and subtracting? 'Trick' methods... very often... can introduce principles...(100 - 3)n = 100n - 3n...is to make use of the distributive property... though... we do not have to put this in such technical language in the classroom."