# Lesson 13

Center Day 2

## Warm-up: Number Talk: Within 20 (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit understandings students have for adding and subtracting within 20 using the strategy of making a ten.

### Launch

• Display one expression.
• “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

### Activity

• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Find the value of each expression mentally.

• $$10 + 4$$
• $$9 + 4$$
• $$9 + 6$$
• $$15 – 6$$

### Activity Synthesis

• “Did anyone approach the problem in a different way?”

## Activity 1: Centers: Choice Time (20 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice working with tens and ones. Students choose from any stage of previously introduced centers.

• Grab and Count
• Five in a Row
• Check It Off

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from previous centers:
• Grab and Count, Stage 2
• Five in a Row, Stages 1–4
• Check It Off, Stages 1–3

### Launch

• Groups of 2
• “Now you are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do first.”
• 30 seconds: quiet think time

### Activity

• Invite students to work at the center of their choice.
• 8 minutes: center work time
• “Choose what you would like to do next.”
• 8 minutes: center work time

Choose a center.

Grab and Count

Five in a Row

Check It Off

### Activity Synthesis

• “Han is playing Check It Off. He picks the numbers 70 and 20. What numbers could he check off?” (50 or 90)

## Activity 2: Centers Choice Time (20 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice adding and subtracting within 20. Students choose from any stage of previously introduced centers.

• How Close?
• Number Puzzles
• Shake and Spill

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from previous centers:
• How Close, Stages 1 and 2
• Number Puzzles, Stages 1 and 2
• Shake and Spill, Stages 3–5

### Launch

• Groups of 2
• “Now you are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Think about what you would like to do first.”
• 30 seconds: quiet think time

### Activity

• Invite students to work at the center of their choice.
• 8 minutes: center work time
• “Choose what you would like to do next.”
• 8 minutes: center work time

Choose a center.

How Close?

Number Puzzles

Shake and Spill

### Activity Synthesis

• Display 8, 4, 1, 7, 5.
• “Priya is playing How Close. Which three numbers should she choose to get close to 20?”

## Lesson Synthesis

### Lesson Synthesis

“How did you and your partner work together during centers? What went well? What can we continue to work on?”