# Lesson 21

Center Day 3

## Warm-up: What Do You Know About 20? (10 minutes)

### Narrative

The purpose of this What Do You Know About _____? is to invite students to share what they know and how they can represent the number 20.

### Launch

• Display the number 20.
• “What do you know about 20?”
• 1 minute: quiet think time

### Activity

• Record responses.

### Student Facing

What do you know about 20?

### Student Response

For access, consult one of our IM Certified Partners.

### Activity Synthesis

• “What connections do you see between different answers?”
• Pick two addition expressions that use different addends and ask, “How are these two expressions related?”

## Activity 1: Introduce How Close? Add to 20 (20 minutes)

### Narrative

The purpose of this lesson is for students to learn stage 1 of the center, How Close? Students pick a given number of digit cards and then choose a subset of those to make an expression that yields a number as close as possible to 20.

### Required Materials

Materials to Gather

Materials to Copy

• How Close? Stage 1 Recording Sheet

### Launch

• Groups of 2
• Give each group a set of number cards, two recording sheets, and access to double 10-frames and connecting cubes or two-color counters.
• “We are going to learn a game called How Close? Add to 20. Let's play the first round together.”
• “First we take out any card that has the number 10. We will not use those cards for the game.”
• Display 5 cards.
• “I can choose two or three of these cards to add to get as close to 20 as I can. What cards should I choose?”
• 1 minute: quiet think time
• 2 minutes: partner discussion
• Share responses.
• “I write an equation with the numbers I chose and the sum of the numbers.”
• Demonstrate writing the equation on the recording sheet.
• “The person who gets a sum closer to 20 gets a point for the round. Then you each get more cards so you always have five cards to choose from. Play again. The person who gets more points wins.”

### Activity

• 10 minutes: partner work time

### Activity Synthesis

• Invite students to share their methods for making a sum close to 20.

## Activity 2: Introduce Five in a Row, Add 7, 8, or 9 (20 minutes)

### Narrative

The purpose of this activity is for students to learn stage 3 of the Five in a Row center. Students choose to add 7, 8, or 9 to the number on their card and then place their counter on the sum on the gameboard. The first partner to have five counters in a row wins.

MLR8 Discussion Supports. Synthesis: For each method that is shared, invite students to turn to a partner and restate what they heard using precise mathematical language.
Action and Expression: Develop Expression and Communication. Give students access to manipulatives such as connecting cubes, counters, or 10-frames.
Supports accessibility for: Conceptual Processing, Memory

### Required Materials

Materials to Gather

Materials to Copy

• Five in a Row Addition and Subtraction Stage 3 Gameboard

### Launch

• Groups of 2
• “We are going to learn a new way to play Five in a Row.”
• Display the gameboard and pick a number card.
• “I can decide to add 7, 8, or 9 to the number on this card. What should I add?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.
• Choose 7, 8, or 9 to add to the number and find the sum.
• Now I put a counter on the sum on the gameboard. Then it is my partner's turn. Continue playing until someone gets five counters in a row.

### Activity

• 10 minutes: partner work time

### Activity Synthesis

• “What method did you see your partner use to decide whether to add 7, 8, or 9?”

## Lesson Synthesis

### Lesson Synthesis

“Today we learned two new games we can play during center time.”

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