The numbers game
Question: If you add up all the digits of a number and keep on adding the
resulting digits until you are left with a single digit, then if the original
digit is divisible by 3, so is the resultant digit. Thus for 129, 1 + 2 + 9 =
12, 1 + 2 = 3. Or 81, where 8 + 1 = 9. Conversely, if the original number is not
divisible by 3, then neither is the resultant digit. Thus for 131, 1 + 3 + 1 =
5.
I have written a computer program that tested this rule right up to 1 billion
and it found…
