Digit sum
Digit sum helps children practise adding the digits of a number to find its digit sum — and using it to check divisibility by 3 and 9. Read the short guide and look through the examples before choosing online practice or a printable worksheet.
How to solve this
- The digit sum of a number is found by adding all its digits: the digit sum of 347 is 3 + 4 + 7 = 14.
- If the digit sum is still more than one digit, add those digits again: 14 → 1 + 4 = 5.
- Check: a number is divisible by 3 (or 9) exactly when its digit sum is divisible by 3 (or 9).
Examples
Digit sum of 347
14
Digit sum of 508
13