With semi-written calculation, you split the numbers into tens and ones.
Example: 47 + 25 split up
47 + 25 = 40 + 20 + 7 + 5
= 60 + 12
= 72
When subtracting, you split only the second number: take away the hundreds and tens first, then the ones.
738 − 264 (264 = 260 + 4): first 738 − 260 = 478, then 478 − 4 = 474
The numbers filled in show the solution.
Example
For parents
What does this exercise practice?
This exercise strengthens place-value understanding and shows a flexible calculation method before the written method is introduced.
Common pitfalls
Children sometimes forget to add the carried-over ones back to the tens sum. Have them explain the calculation steps out loud.
How to practice at home
Do mental math in pairs, one solves it semi-written, the other checks.
Related: Number Sentences with a Gap, Written Addition, Semi-written Multiplication