With bigger numbers the same trick from up to 100 helps you. You split the second number so that you first reach the next ten and then add the rest.
Example: 592 + 9
592 + 9 = 592 + 8 + 1
= 600 + 1
= 601
The numbers filled in show the solution.
Example
592 + 9 = 592 + 8 + 1 = 10 + 1 = 601
478 + 7 = 478 + 2 + 5 = 10 + 5 = 485
For parents
What does this exercise practice?
This exercise transfers crossing the ten from numbers up to 100 to bigger numbers and reinforces the splitting strategy.
Common pitfalls
Children sometimes mix up the two steps and do not add up to the full ten first. Have them show you how much is missing to reach the next ten.
How to practice at home
Take turns naming three-digit numbers plus a small number and calculate across the ten together.
Related: Calculation, Semi-written, Written +