An elementary check of a Multiplication which makes use of the Congruence (mod 9) for . From this Congruence, a Multiplication must give

so must be (mod 9). Casting out nines is sometimes also called ``the Hindu Check.''

**References**

Conway, J. H. and Guy, R. K. *The Book of Numbers.* New York: Springer-Verlag, pp. 28-29, 1996.

© 1996-9

1999-05-26