# Mental addition and subtraction (age 9+)

Add and subtract numbers mentally with increasingly large numbers, using place-value knowledge and derived facts

Builds on: Mental addition and subtraction (age 7+) (hard, https://ai.page/c/mental-addition-and-subtraction-age-7/en.md), Place Value × 10 Pattern (soft, https://ai.page/c/place-value-10-pattern/en.md)

Concept id: mental-addition-and-subtraction-age-9. Subject: maths. Licence: CC BY-SA 4.0.

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