Question

why we have assume 9 instead of 3

http://in.answers.yahoo.com/question/index?qid=20100623061943AAi60Kw

Answer 1

@PeterPan

Answer 2

Because you only have to consider 3 cases, that way?

Answer 3

is there any other specific reason

Answer 4

No. I guess you could use mod 9, but then again, you'd take 9 cases.
3 is best, because it's the only prime-factor of 9, and therefore, 9 would come more naturally to it.

considering mod 2 would be insufficient, and probably inconclusive.

Answer 5

k
thank u