# Addition & Subtraction to 20: Strategies and Basic Facts

#### Learning Goal

Develop knowledge of a network of number relationships and apply that knowledge to addition and subtraction in the range 1 to 20

#### Learning Goal Description

An emphasis on number relationships refines and extends the use of non-count-by-one strategies to support a path to fluency for addition and subtraction facts to 20. Building upon strategies for addition and subtraction in the range to 10, the learning progression includes key combinations and partitions, relational thinking, strategy development, and targeted practice. Instruction advances from the use of physical models to the development of mental models. This knowledge creates a strong foundation for mental addition and subtraction in the range to 100.

#### Pre-Requisite Knowledge

Students should have facility with the number words and numerals to at least 20. Students should have facility with addition and subtraction in the range to 10 using non-count-by-one strategies.
(see Ready Set Math modules Early Numeracy: Words, Symbols, and Quantities and Addition & Subtraction: Strategies and Basic Facts to 10

#### Sub-goal A

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#### Sub-goal B

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#### Sub-goal C

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#### Sub-goal D

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Wright, R. J., Stanger, G., Stafford, A. K., & Martland, J. (2015). Teaching number in the classroom with 4-8 year olds (2nd ed.). London: Sage Publications, Ltd. (Chapter 7)

Wright, R. J., Ellemor-Collins, D., & Tabor, P. D. (2012). Developing number knowledge: Assessment, teaching & intervention. London: Sage Publications, Ltd. (Chapter 4)

The knowledge developed in this module, along with knowledge relating to working with base-10 units, can support the development of mental strategies for addition and subtraction in the range to 100.

(see Ready Set Math modules Place Value: Counting Involving Base-Ten Units and Addition & Subtraction to 100: Mental Strategies

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