# Lesson 10

Center Day 2

## Warm-up: True or False: Adding within 100 (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies students have for using place value understanding to add. These understandings help students deepen their understanding of the properties of operations and will be helpful later when students add within 100.

### 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 strategies.
• Repeat with each equation.

### Student Facing

Is each statement true or false?
Be prepared to explain your reasoning.

• $$24 + 30 = 44$$
• $$24 + 40 = 64$$
• $$30 + 45 = 75$$
• $$32 + 45 = 76$$

### Activity Synthesis

• “Some students said they added the tens to the tens and the ones to the ones. Think about using this method when you add during center time today.”

## Activity 1: Introduce Estimate and Measure, Choose Your Unit (20 minutes)

### Narrative

The purpose of this activity is for students to learn a new center called Estimate and Measure, Choose Your Unit. Students choose an object and a familiar unit to measure it with. They estimate the measurement of the object and then measure to find the actual length to the nearest whole length unit.

### Required Materials

Materials to Gather

Materials to Copy

• Estimate and Measure Stage 1 Recording Sheet

### Required Preparation

• Gather or identify objects of various lengths that are less than 20 connecting cubes long (pencils, markers, books, glue, scissors, shoe, tape dispenser).

### Launch

• Groups of 2
• Give each group access to objects they can measure as well as various measuring units.
• “We are going to learn a new center called Estimate and Measure, Choose Your Unit. In this activity, you choose an object that you will measure. Then you choose the unit you would like to use to measure the object. Record the object and the unit you will use to measure. Before measuring the object, make an estimate of the object’s length. Record your estimate. Then measure the object and record the actual measurement.”

### Activity

• 15 minutes: partner work time

### Activity Synthesis

• Display an object measured with gaps between some of the length units.
• “What feedback could you give to someone who measured like this?” (There should not be any gaps.)
• Display an object measured with different length units such as base-ten cubes and connecting cubes.
• “What feedback could you give to someone who measured like this?” (You have to use the same object to measure the entire length of the object. You can't use small and big cubes, you have to choose one.)

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

### Narrative

The purpose of this activity is for students to choose from activities that focus on adding within 100. Students choose from any stage of previously introduced centers.

• How Close?
• Target Numbers
• Five in a Row
MLR8 Discussion Supports. Synthesis: Provide students with the opportunity to rehearse what they will say with a partner before they share with the whole class.
Action and Expression: Develop Expression and Communication. Provide access to a variety of tools such as connecting cubes in towers of 10 and singles and mini-whiteboards.
Supports accessibility for: Attention, Organization

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from:
• How Close? Stages 1–3
• Target Numbers, Stages 1–3
• Five in a Row, Stages 1–6

### Launch

• Groups of 2
• “Now you will 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?

Target Numbers

Five in a Row

### Activity Synthesis

• “What method of adding did you use most today?” (I added tens to tens and ones to ones. I composed a ten.)

## Lesson Synthesis

### Lesson Synthesis

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