divisibility rule for 3

Rule:
A number is divisible by 3,if the sum of its digits is divisible by 3.
Example 1:
Is 567894 divisible by 3?
Solution:
The sum of digits in the number 567894 is 39.
39 is divisible by 3 since 39/3=13.
According to the rule given above,the number 567894 is divisible by 3.
Example 2:
Is 782342 divisible by 3?
Solution:
The sum of digits in the number 782342 is 26.
26 is not divisible by 3 since 26/3 leaves 2 as remainder.
As per the rule given above,the number 782342 is not divisible by 3.