<< Casting out nines ? http://mathforum.org/library/drmath/view/72752.html

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No. Casting out nines is the (oldish) name for the *procedure* used to obtain the digital root, not that digit itself. << "check digit" ? http://en.wikipedia.org/wiki/Check_digit www.math.unl.edu/~mbrittenham2/classwk/203f07/quiz/203words1.pdf "http://math.boisestate.edu/~tconklin/MATH124/Main/Readings/3 Number Theory/PDFs/Number Theory/Modular Arithmetic in the Marketplace.pdf"

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No. The remainder mod 9 is only one of many types of "check digits", so that is not its name. --Dan ________________________________________________________________________________________ "Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read." --Groucho Marx