"Prove that a positive integer, expressed as a decimal (or base 10) expansion, is divisible by 3 if and only if the sum of the digits is divisible by 3."
I'm totally stuck where to start, hints only please!
Number Theory watch
- Thread Starter
- 10-11-2008 17:17
- 10-11-2008 17:23
consider "bc" = 10b+c = 9b+b+c. should be a good hint for you to work out the general case.