# Lesson 10

Center Day 2

## Warm-up: Choral Count: Count by 10 (10 minutes)

### Narrative

The purpose of this Choral Count is to invite students to practice counting by 10 and notice patterns in the count. These understandings help students develop fluency with the count sequence. When students notice the pattern in the ones place as they count by 10, they are looking for and making use of structure (MP7).

### Launch

• “Count by 10, starting at 0.”
• Record as students count.
• Stop counting and recording at 100.

### Activity

• “What patterns do you see?”
• 1–2 minutes: quiet think time
• Record responses.

### Activity Synthesis

• “How is counting by 10 like counting by 1?”
• “Who can restate the pattern in different words?”
• “Does anyone want to add an observation on why that pattern is happening here?”
• “Do you agree or disagree? Why?”

## Activity 1: Revisit What’s Behind My Back, 10 Cubes (20 minutes)

### Narrative

The purpose of this activity is for students to revisit a center from kindergarten. In this center, What’s Behind My Back, students find the missing part to make 10. They record different ways to make 10 with equations.

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.
Representation: Internalize Comprehension. Synthesis: Record students’ methods for finding the missing part on a visual display.
Supports accessibility for: Conceptual Processing, Attention

### Required Materials

Materials to Gather

Materials to Copy

• What's Behind My Back Stage 2 Recording Sheet Grade 1

### Required Preparation

• Each group of 2 needs 10 connecting cubes.

### Launch

• Groups of 2
• Give each group two recording sheets, ten connecting cubes, and access to 10-frames and two-color counters.
• “We are going to play a game you learned in kindergarten called What’s Behind My Back. Let’s play the first round together to make sure we all remember how to play.”
• Demonstrate starting with a tower of ten cubes.
• “Each group will start with a tower of ten cubes. Then one partner will break the tower into two parts and hide one of the parts behind their back.”
• Break the tower into two parts and hide one part behind your back. Show the other part to the class.
• “The other partner will write an equation leaving a blank box for the missing number.”
• Demonstrate writing $$4 + \boxed{\phantom{\frac{aaai}{aaai}}} = 10$$.
• “Then they will figure out how many cubes are hidden behind their partner’s back. You may use 10-frames and two-color counters if they are helpful. How many cubes are behind my back?”
• Share responses.
• “When you agree on how many are hiding, you can complete the equation.”
• Demonstrate filling in the missing number in the equation.

### Activity

• “Now you will play with your partner. Take turns breaking the tower and hiding one part behind your back.”
• 10 minutes: partner work time
• Monitor for students who use a 10-frame or their fingers to figure out how many cubes are hiding.

### Activity Synthesis

• Invite previously identified students to share.
• “How did you figure out how many cubes were hiding behind your partner’s back?”

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

### Narrative

The purpose of this activity is for students to choose activities focusing on adding and subtracting within 10. Students choose from three centers introduced in the previous section and one introduced in the previous activity.

• What’s Behind My Back
• Five in a Row: Addition and Subtraction
• Check it Off
• Find the Pair

Students may work with more than one center during this time. Keep the materials from each center organized to use in future lessons.

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from previous centers:
• What’s Behind My Back, Stage 2
• Five in a Row: Addition and Subtraction, Stages 1 and 2
• Check it Off, Stages 1 and 2
• Find the Pair, Stage 2

### Launch

• Groups of 2
• “Now we 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

### Student Facing

Choose a center.

Five in a Row: Addition and Subtraction

Check it Off

What's Behind My Back

Find the Pair

### Activity Synthesis

• “How do you know that the center you chose was a good choice?”