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