# Lesson 16

Center Day 3

## Warm-up: Number Talk: Add 20 and 1 (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 100. Students use their understanding of the properties of operations and place value as they notice the relationship between the expressions and why they have the same value (MP7).

### 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

• Record answers and strategies.
• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Find the value of each expression mentally.

• $$65 + 20$$
• $$85 + 1$$
• $$65 + 20 + 1$$
• $$65 + 21$$

### Activity Synthesis

• “Why do the last three expressions all have the same value?” (They are all adding $$65 + 20 + 1$$ in different ways.)

## Activity 1: Introduce Counting Collections, Estimate and Count Up to 120 (20 minutes)

### Narrative

The purpose of this activity is for students to learn stage 3 of the Counting Collections center. Students are given a collection of up to 120 objects. They record an estimate for how many objects they think are in their collection. Then, they work with a partner to figure out how many objects are in their collection. Each partner records how many. Students may draw pictures, write numbers or equations, or use base-ten representations to represent their collection.

Representation: Access for Perception. Students may benefit from hearing the instructions for the centers more than once.
Supports accessibility for: Attention, Memory

### Required Materials

Materials to Gather

Materials to Copy

• Counting Collections Stage 3 Recording Sheet

### Required Preparation

• Create a collection of up to 120 objects per group of 2 students (buttons, two-color counters, linking cubes, paper clips, pattern blocks, square tiles).

### Launch

• Groups of 2
• Give each group two recording sheets, a collection of objects, and access to tools to help organize their count.
• “We are going to do more Counting Collections.”
• “This time, you will estimate how many objects are in your collection before you count them. Record your estimate, then count the collection. Record your count.”

### Activity

• 15 minutes: partner work time time

### Activity Synthesis

• “How did you organize the objects in your collection as you counted?”

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

### Narrative

The purpose of this activity is for students to practice measuring lengths and writing numbers up to 120.

Students choose from any stage of previously introduced centers.

• Write Numbers
• Estimate and Measure
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.

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from:
• Write Numbers, Stages 1–3
• Estimate and Measure, Stage 1

### Launch

• Groups of 2
• “Now you are going to work on 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.

Write Numbers

Estimate and Measure

### Activity Synthesis

• Display numbers 108, 109, 110, 111, 112.
• “What do you notice about these numbers?” (They all have 100. Some have a zero and some don’t. The numbers go in order 8, 9, 10, 11, 12.)

## Lesson Synthesis

### Lesson Synthesis

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