# Lesson 12

Decompose Area

### Lesson Purpose

The purpose of this lesson is for students to apply what they know about multiplication of whole numbers and fractions to decompose a rectangle to find its area.

### Lesson Narrative

In previous lessons, students found the area of rectangles with one whole number side length and one fractional side length.
The purpose of this lesson is for students to apply what they know about decomposing rectangles with whole number side lengths to represent and find the area of rectangles with a mixed number side length. Students first find the area in a way that makes sense to them and then analyze different strategies for finding area.

• Engagement
• MLR1

### Learning Goals

Teacher Facing

• Decompose a rectangle to find its area.

### Student Facing

• Let's decompose rectangles to find their area.

### Lesson Timeline

 Warm-up 10 min Activity 1 20 min Activity 2 15 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

What question do you wish you had asked today? When and why should you have asked it?

### Suggested Centers

• How Close? (1–5), Stage 7: Multiply Fractions and Whole Numbers to 5 (Addressing)
• Rectangle Rumble (3–5), Stage 3: Factors 1–10 (Supporting)