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Lesson Plan
Composing and Decomposing
Use this lesson to introduce composing and decomposing as part of your students’ addition and subtraction toolkits.
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Subject
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Learning Objectives
Students will be able to compose and decompose numbers within 20.
The adjustment to the whole group lesson is a modification to differentiate for children who are English learners.
Introduction
(2 minutes)
- Ask students if they know the meaning of compose. Write it on the chart paper. Define it as coming together to make something. For example, Four is composed of four ones.
- Ask students if they can now guess the meaning of decompose. Write it on the chart paper. Define it as to separate into smaller or simpler parts. For example, the number 42 can be decomposed into four tens and two ones.
- Explain that today students will be composing and decomposing numbers within 20. Elaborate that these skills will help us add and subtract.
Beginning
- Define vocabulary words in English and student's home language (L1).
- Help students design visuals that illustrate the concept of decomposing and composing (ie. breaking something into smaller parts and putting something back together).
Intermediate
- Challenge students to explain decomposing and composing in their own words to a partner.
- Encourage students to reflect on how learning to decompose and compose will help them add and subtract.
- Provide sentence stems, such as:
- Learning to break numbers down (decompose) will help me because ________.
- Learning how to put numbers together (compose) will help me because ________.