Every addition problem has matching subtraction problems, and the other way around!
From plus to minus:
235 + 120 = 355, so 355 - 120 = 235.
Always write the matching inverse problem next to it.
The numbers filled in show the solution.
Example
235 + 121 = 356
356 − 121 = 235
356 − 235 = 121
452 − 131 = 321
321 + 131 = 452
131 + 321 = 452
For parents
What does this exercise practice?
This exercise shows that addition and subtraction are inverse operations. Understanding this lets children check their work and find their own mistakes.
Common pitfalls
Children often just flip the operation sign but mix up the positions of the numbers. Saying it out loud helps: 355 minus 120 is 235, so 235 plus 120 is 355.
How to practice at home
Write down an addition problem and find the two matching subtraction problems together. This turns checking into a habit.
Related: Calculation, Written −