# Lesson 14

Center Day 2 (optional)

## Warm-up: True or False: Is This 50? (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies students have for reasoning about place value to determine if an equation is true or false. The reasoning students do here helps to deepen their understanding of using strategies based on place value. It will also be helpful later when students reason about how to reach 100 from a given number using the number line.

### Launch

- Display one statement.
- “Give me a signal when you know whether the statement is true and can explain how you know.”
- 1 minute: quiet think time

### Activity

- Share and record answers and strategy.
- Repeat with each statement.

### Student Facing

Decide if each statement is true or false. Be prepared to explain your reasoning.

- \(28 + 2 + 20 = 50\)
- \(16 + 3 + 30 = 50\)
- \(36 + 4 + 20 = 50\)

### Student Response

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### Activity Synthesis

- “How can you explain your answer to the last statement without finding the sum of all three addends?” (I could add 36 and 20 and see that it’s more than 56. I could add 36 and 4 to get 40. I know I would need 10 more to get to 50 and I see more than 10 left to add.)

## Activity 1: Introduce Jump the Line, Add and Subtract within 100 (20 minutes)

### Narrative

The purpose of this activity is for students to learn stage 1 of the Jump the Line center. In this stage, students take turns making strategic choices about numbers to add or subtract to reach target numbers. Students choose 3 target numbers and mark them on the number line. Both players start at the beginning of the number line. They spin all 3 spinners and decide which of the moves they want to use on their turn. Students take turns spinning and moving, trying to land exactly on the target numbers. The first player to land on 2 target numbers wins.

### Required Materials

Materials to Gather

Materials to Copy

- Jump the Line Stage 1 Gameboard
- Jump the Line Stage 1 Spinners

### Launch

- Groups of 2
- Give each group a spinner, paper clip, dry erase marker and gameboard.
- Display spinners and gameboard.
- “You and your partner will choose 3 target numbers and mark them on your number line.”
- “Then you will take turns spinning all 3 spinners. On your turn you can decide which spin to use. Your goal is to jump to one of the numbers you and your partner marked.”
- “The first player to land exactly on 2 of the target numbers wins.”
- Play a round with the class, if needed.

### Activity

- 15 minutes: partner work time

### Activity Synthesis

- Display a gameboard with 3 target numbers. Spin the three spinners.
- “This is my gameboard and my spins. Which spin would you use? Why?”

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

### Narrative

The purpose of this activity is for students to choose from activities that focus on addition or subtraction. Students choose from any stage of previously introduced centers.

- Jump the Line
- Number Line Scoot
- How Close?

### Required Materials

Materials to Gather

### Required Preparation

Gather materials from:

- Jump The Line, Stage 1
- Number Line Scoot, Stage 1
- How Close, Stage 3

### Launch

- “Now you will choose from centers we have already learned. One of the choices is to continue with Jump the Line.”
- 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

### Student Facing

Choose a center.

Jump the Line

Number Line Scoot

How Close?

### Activity Synthesis

- “What did you like about the activity you worked on today?”