Unit 4, Lesson 19
Compose and Decompose to Add and Subtract
Grade 4
Preparation
Lesson Narrative
In earlier grades, students encountered subtraction problems which required decomposing a unit. In this lesson, students review this idea of decomposition and revisit how it is recorded when using the standard algorithm to subtract numbers through the thousands place. Students also use composition to add multi-digit numbers through the hundred-thousands place.
- Representation
None
- Interpret (orally) recording methods for showing composed and decomposed units.
- Use the standard algorithm to add and subtract multi-digit numbers.
- Let’s compose and decompose units to add and subtract.
Required Materials
Activity 1
Required Preparation
None
Teacher Reflection Questions
Who got to do math today in class? How do you know? What norms or routines allowed those students to engage? How can you adjust these norms and routines so all students do math tomorrow?