Lesson 19
Compose and Decompose to Add and Subtract
Lesson Purpose
The purpose of this lesson is for students to review how to add and subtract multi-digit numbers with composition and decomposition.
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
Learning Goals
Teacher Facing
- Add and subtract multi-digit numbers, with composing or decomposing, using the standard algorithm.
Student Facing
- Let’s compose and decompose units to add and subtract.
Required Materials
Materials to Gather
Required Preparation
CCSS Standards
Addressing
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 15 min |
| Activity 2 | 20 min |
| Lesson Synthesis | 10 min |
| Cool-down | 5 min |
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?
Suggested Centers
- Tic Tac Round (3–5), Stage 2: Any Place (Addressing)
- Number Puzzles: Addition and Subtraction (1–4), Stage 6: Beyond 1,000 (Addressing)