# Lesson 5

Center Day 1

### Lesson Purpose

The purpose of this lesson is for students to practice adding and subtracting a multiple of 10 from a multiple of 10 and to practice adding and subtracting within 20.

### Lesson Narrative

In Activity 1, students learn stage 3 of the Check It Off center. In this new stage, called Add or Subtract Tens, students pick two number cards that are multiples of 10 (0–90) and choose whether to make an addition or subtraction expression. In Activity 2, students choose from previously introduced centers that also focus on adding and subtracting.

• Action and Expression
• MLR8

### Learning Goals

Teacher Facing

• Add and subtract multiples of 10 from multiples of 10.
• Add and subtract within 20.

### Required Materials

Materials to Gather

Materials to Copy

• Number Cards, Multiples of 10 (0-90)
• Check It Off Stage 3 Recording Sheet

### Required Preparation

Activity 1:

• Create a set of cards from the blackline master for each group of 2.

Activity 2:

• Gather materials from previous centers:
• Five in a Row, Stages 1–4
• How Close, Stages 1 and 2
• Number Puzzles, Stages 1 and 2

### Lesson Timeline

 Warm-up 10 min Activity 1 15 min Activity 2 25 min Lesson Synthesis 10 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?