Mental addition and subtraction (age 9+)

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

Usually learned at ages 9–10

Builds on: Mental addition and subtraction (age 7+), Place Value × 10 Pattern (helps)

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On the map from: Marble Skill Taxonomy (v1), © Generative Spark, Inc. (withmarble.com), text CC BY-SA 4.0, database ODbL 1.0: https://github.com/withmarbleapp/os-taxonomy