Determining whether a number is divisible by 3 is a simple process based on the sum of its digits. Here’s how you can do it:
- Identify the Number: Start with the number you want to check. For example, let’s take the number 123.
- Sum the Digits: Next, add together all the individual digits of that number. For 123, you would calculate 1 + 2 + 3, which equals 6.
- Check for Divisibility: Now, take the sum you obtained (in this case, 6) and see if it is divisible by 3. Dividing 6 by 3 gives you 2, with no remainder, which means 6 (and therefore 123) is divisible by 3.
This rule works for any size of number, from a single-digit number to a lengthy number with many digits. For instance, if you have the number 987654321, you would add the digits: 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 45, and since 45 is divisible by 3 (45 ÷ 3 = 15), you can conclude that 987654321 is also divisible by 3.
Overall, this method is both efficient and easy to execute, making it a useful trick for mental math as well as for quick calculations!