# Lesson 19

Compongamos y descompongamos para sumar y restar

### 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

• Compongamos y descompongamos unidades en base diez para sumar y restar.

### Required Materials

Materials to Gather

### 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)