## If the Sum of the Digits of a Number is Divisible by Three, the Number Is Divisible by Three

Take a two-digit base-10 number where the digits are represented by ab. This number is equal to 10a + b and the sum of its digits are a + b. The difference between the number and the sum is 9a, which is divisible by three. So a + b is divisible by three, if and only… Read More »