When you calculate this way, you break the numbers apart into tens and ones.
Example: 45 + 28 broken apart
45 + 28 = 40 + 20 + 5 + 8
= 60 + 13
= 73
The numbers filled in show the solution.
Example
45 + 28 =
= 40 + 20 + 5 + 8
= 60 + 13
= 73
36 + 29 =
= 30 + 20 + 6 + 9
= 50 + 15
= 65
For parents
What does this exercise practice?
This exercise strengthens place-value understanding and shows a flexible way to calculate before the column method comes.
Common pitfalls
Children sometimes forget to add the carry from the ones back to the sum of the tens. Have them explain their steps in words.
How to practice at home
Do mental math in pairs: one breaks the numbers apart, the other checks.
Related: What does multiplying mean?, Column addition, Adding across the ten