Inverse: addition undoes subtraction
Recognise and use the inverse relationship between addition and subtraction to check calculations and solve missing-number problems
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Teaching Table · Plan outline
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“If your child 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?”
Full guide and materials
- Activity. Recognise and use the inverse relationship between addition and subtraction to check calculations and solve missing-number problems
What to notice. 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
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If your child 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?
Recognise and use the inverse relationship between addition and subtraction to check calculations and solve missing-number problems
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Learning resources
Reviewed external links that reinforce this concept. They do not replace Gakuva’s teaching approach.
Toy Theater · Practice link — not the full lesson
Number Bonds — adult-guided supplementary tool
Place a whole and two parts in a number-bond diagram; say the related equations.
Adult must supply questions and judge answers · No automatic marking or saved progress established · Ads · No login/payment in recorded test; access can change.
Review and open practice
A supplementary manipulative, not an automatically marked game. Mobile/touch, audio and drawing tools were not verified.
Opening this link does not save learning or assess mastery.
Open practice (new tab)Parent tips
Try a whole of 9 and one part of 4. Find 5, then explain 4 + 5 = 9 and 9 − 4 = 5. Ask how subtraction undoes addition. This check is parent-led.
Source, access and review notes
Use a number-bond diagram with an adult to explore how addition and subtraction undo one another. Place the whole and its two parts, then say the related equations.
Adult-guided supplementary tool; a manipulative, not an automatically marked game. No automatic correctness feedback, saved progress, or independent learner explanation was established. Parent prompt: “We have 9 altogether and one part is 4. What is the missing part? Show 4 + 5 = 9, then use 9 − 4 = 5 to check. Explain how subtraction undoes the addition.”
Tested number placement required no login or payment. Advertisement labels observed. An adult must supply questions and judge the explanation. Mobile/touch, audio, and drawing tools were not verified. Access and advertisements can change.
Unknown — link only
Check 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
“If your child 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?”
Curriculum record
- Type
- Conceptual
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 6–7
Standards