Use the theorem below to answer the question that follows.
If the sum of a number's digits is divisible by three, the number is divisible by three.
Which of the following ways of expressing a three digit number, n, best demonstrates why this theorem is true?
I'll do my best. I'm thinking...
99 is divisible by 3. So if a(99 + 1) is divisible by 3, then a must be divisible by 3. Same goes for the b term.
...am I heading the right direction? Because c could be anything. So I don't see what that proves.