Sum of Digits.

[Dieter]

(03-26-2016 01:17 PM)ggauny@live.fr Wrote:  But may be you are right, I dont' know.
I think it is very difficult to answer for me.

The solution is quite easy. Take a look here (Français) or here (English) or here (Deutsch).

That's why checking whether a number is divisible by 3 is so easy: just add its digits and check if that sum can be divided by 3. The sum is the remainder of a division by 9. So if this remainder is 0, 3 or 6 the number can also be divided by 3.

Dieter