Semi-formal addition
On this page children practise adding three-digit numbers using a split-by-place-value method that bridges mental and written arithmetic. Start with the short method and the examples, then use the online practice or print a worksheet with answers.
How to solve this
- Semi-formal addition means writing the partial sums line by line: add hundreds, then tens, then ones, then combine.
- This method makes every carry visible and helps avoid errors when numbers are complex.
- Check by adding in the opposite direction (ones first, then tens, then hundreds) and confirming the same total.
Examples
347 + 286 (semi-formal)
633
428 + 159 (semi-formal)
587
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.
- 125 + 486 = ___
- 466 + 453 = ___
- 158 + 109 = ___
- 224 + 282 = ___
- 132 + 360 = ___
- 186 + 260 = ___
- 114 + 394 = ___
- 457 + 358 = ___
Show answers
- 611
- 919
- 267
- 506
- 492
- 446
- 508
- 815