Final answer:
To check if a number is divisible by 3, add all the digits together; if the sum is divisible by 3, then the original number is also divisible by 3.
Step-by-step explanation:
Divisibility by 3
To determine if a number is divisible by 3, you can use a simple test. Add up all the digits in the number. If the sum of the digits is divisible by 3, then the original number is also divisible by 3.
This is because the number 3 has a property where multiples of it have a digit sum that is also a multiple of 3. For example, with the number 231, you add 2 + 3 + 1 to get 6. Since 6 is a multiple of 3, we can say that 231 is divisible by 3.
This rule is useful when working with large numbers as it allows for a quick check without having to perform long division.