# Lesson 8

Compose Tens and Hundreds to Add

### Lesson Purpose

The purpose of this lesson is for students to add within 1,000 using place value-based strategies by composing both a ten and a hundred.

### Lesson Narrative

In previous lessons, students related composing a ten and a hundred when adding within 1,000. They found sums that required composing one larger unit when adding by place. Throughout this lesson, the addends in each expression encourage students to consider adding by place. Both activities invite students to make sense of methods based on adding by place and to use the method that makes the most sense to them. Monitor for the different methods students use and how they use their understanding of place value to add and make sense of others' work (MP3, MP7).

• Action and Expression

### Learning Goals

Teacher Facing

• Add a two-digit number to a three-digit number using place value strategies that include composing units.

### Student Facing

• Let’s compose tens and hundreds to add.

### Required Materials

Materials to Gather

### 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

Today students composed a ten and a hundred when adding a two-digit number and a three-digit number for the first time. Where did you observe students generalizing their understanding of place value and composing larger units as they found the sums? How will you support students who prefer other methods to make sense of composing units when adding by place as they continue this work in upcoming lessons?

### Suggested Centers

• Five in a Row: Addition and Subtraction (1–2), Stage 7: Add within 1,000 without Composing (Addressing)
• Number Puzzles: Addition and Subtraction (1–4), Stage 4: Within 100 with Composing (Supporting)