# Lesson 15

Number Talk

### Lesson Purpose

The purpose of this lesson is for students to apply their understanding of addition and subtraction to create a Number Talk activity.

### Lesson Narrative

This lesson provides an opportunity to observe the ways in which students make use of structure and repeated reasoning to design a Number Talk. The warm-up is followed by four Number Talk activities. In the first activity, students are given three expressions and asked to write the missing expression. In each of the subsequent activities, one additional expression is missing. In the last activity, students write all four expression of a Number Talk.

It is not essential that students complete all four activities. Decide which activities to do based on how much scaffolding students may need. The lesson may take more than one day, especially if students facilitate their Number Talk with other groups.

If students need additional support with the concepts in this lesson, refer back to Unit 3, Sections A and B in the curriculum materials.

• Action and Expression
• MLR8

### Learning Goals

Teacher Facing

• Apply understanding of addition and subtraction within 1,000 to create a Number Talk activity.

### Student Facing

• Let’s create a Number Talk activity.

Building On

### Lesson Timeline

 Warm-up 10 min Activity 1 15 min Activity 2 15 min Activity 3 15 min Activity 4 15 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

What do your students think it means to be good at math? How are you helping them change negative impressions they might have about their ability to reason mathematically?