Mathematics·Addition & Subtraction·conceptual
Inverse: addition undoes subtraction
Recognise and use the inverse relationship between addition and subtraction to check calculations and solve missing-number problems
Suggested ages 6–7
Learning journey
Your child is building strong foundations in addition and subtraction — learning to add and subtract numbers fluently within 20, understanding the relationship between these operations, and applying various mental strategies to solve problems.
Evidence of understanding
- Check 15 + 7 = 22 by calculating 22 − 7 = 15
- Use the inverse to solve: □ + 9 = 14, so □ = 14 − 9 = 5
- Explain that addition and subtraction 'undo' each other
Assessment prompt
If Inverse: addition undoes subtraction works out 13 + 5 = 18, can they immediately use that to say '18 − 5 = 13' — without having to work the subtraction out all over again?
Standards alignment
1.OA.4US · ccss-math
Subtraction as unknown-addend problem
Common Core State Standards for Mathematics · 1
Maths/Y2/AS/9GB · uk-nc-2013
Inverse relationship
The national curriculum in England: Key stages 1 and 2 framework document · Key Stage 1