Digit sum
On this page children practise adding the digits of a number to find its digit sum — and using it to check divisibility by 3 and 9. Start with the short method and the examples, then use the online practice or print a worksheet with answers.
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
Practice problems with answers
Solve these problems on paper or out loud, then check the answer key. The online practice and the printable worksheet give a new set every time.
- Digit sum of 902
- Digit sum of 555
- Digit sum of 416
- Digit sum of 696
- Digit sum of 981
- Digit sum of 134
- Digit sum of 480
- Digit sum of 681
Show answers
- 11
- 15
- 11
- 21
- 18
- 8
- 12
- 15