With mental math jottings, 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 tens first, then the ones.
73 − 28: first 73 − 20 = 53, then 53 − 8 = 45
The numbers filled in show the solution.
Example
47 + 25 =
= 40 + 20 + 7 + 5
= 60 + 12
= 72
38 + 36 =
= 30 + 30 + 8 + 6
= 60 + 14
= 74
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 with jottings, the other checks.
Related: Number Sentences with a Gap, Written Addition, Mental Multiplication with Jottings