# Lesson 2

Cómo saber si ya contamos (optional)

## Warm-up: Conversación numérica: Sumemos y restemos 0 y 1 (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding and subtracting 0 and 1. These understandings help students develop fluency with the count sequence and adding and subtracting within 5.

When students use their knowledge of the count sequence when they add or subtract 1, they look for and make use of structure (MP7).

### Launch

• Display one expression.
• “Hagan una señal cuando tengan una respuesta y puedan explicar cómo la obtuvieron” // “Give me a signal when you have an answer and can explain how you got it.”
• 1 minute: quiet think time

### Activity

• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Encuentra el valor de cada expresión.

• $$3 + 0$$
• $$3 + 1$$
• $$3 - 1$$
• $$2 - 0$$

### Activity Synthesis

• Display $$3 + 0$$ and $$2 - 0$$.
• “¿En qué se parecen estas expresiones? ¿En qué son diferentes?” // “What is the same about these expressions? What is different about them?” (One is addition and one is subtraction. They both have zero.)

## Activity 1: Contemos colecciones (10 minutes)

### Narrative

The purpose of this activity is for students to count their collection in a way that makes sense to them and keep track of which objects have been counted. Keeping track of which objects have been counted helps students count accurately and ensure they count all of the objects and do not count each object more than once (MP6). Students are provided with 10-frames and counting mats to help them organize their collections.

MLR8 Discussion Supports. Display and read aloud the following sentence frame to support small-group discussion: “Hay ____ objetos en mi colección” // “There are _____ objects in my collection.” Invite students to chorally repeat this sentence in unison 1–2 times.

### Required Materials

Materials to Gather

### Required Preparation

• Each student needs a collection of 11-20 objects.

### Launch

• Groups of 2
• Give each student a collection of objects and access to 10-frames and a counting mat.
• “¿Cuántos objetos hay en su colección?” // “How many objects are in your collection?”

### Activity

• 5 minutes: independent work time
• Monitor for students who use the 10-frame or the counting mat to organize and count their objects.
• “Díganle a su pareja cuántos objetos hay en su colección” // “Tell your partner how many objects are in your collection.”
• 1 minute: partner discussion

### Student Response

If students count each object more than once or do not count some of the objects, consider asking:

• “¿Cuántos objetos tienes? ¿Cómo lo sabes?” // “How many objects do you have? How do you know?”
• Display the counting mat or the 10-frame and ask “¿Como puedes usar este tablero para asegurarte de que contaste cada objeto?” // “How can you use this mat to help you make sure that you count each object?”

These students may benefit from the next activity in this optional lesson.

### Activity Synthesis

• Invite previously identified students to share how they counted their collections.
• “¿Qué observan sobre cómo contaron?” // “What do you notice about how they counted?” (They said one number for each object. They used the counting mat/10-frame to organize their objects. They counted all of the objects one time.)
• After each student shares, write or display the number and say, “Hay _____ objetos en su colección” // “There are _____ objects in their collection.”

## Activity 2: Diferentes maneras de saber si ya contamos (10 minutes)

### Narrative

The purpose of this activity is for students to practice keeping track of the objects that have been counted as they count collections of up to 20 objects. Students may benefit from working on the concepts in this optional activity more than one time.

### Required Preparation

• Each student needs a collection of 11–20 objects.
• Students need the 10-frames and counting mats from the previous activity.

### Launch

• Groups of 2
• Give each student a collection of objects and access to 10-frames and a counting mat.
• Display a 10-frame mat and a counting mat.
• “¿Cómo pueden usar el tablero de conteo para descifrar cuántos objetos hay en su colección?” // “How can you use the counting mat to help you figure out how many objects are in your collection?” (I can put all of the objects on one side and say a number as I move each object to the other side.)
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• Share responses.
• “¿Cómo pueden usar el tablero de 10 para descifrar cuántos objetos hay en su colección?” // “How can you use the 10-frame to help you figure out how many objects there are in your collection?” (I can put one object in each box and line up the rest of the objects. Then I can count them.)
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• Share responses.
• “Escojan el tablero de 10 o el tablero de conteo y úsenlo para descifrar cuántos objetos hay en su colección” // “Choose either the 10-frame or the counting mat to help you figure out how many objects are in your collection.”

### Activity

• 4 minutes: independent work time
• “Busquen un compañero que haya usado una herramienta diferente para contar su colección. Si usaron un tablero de 10 para contar su colección, busquen un compañero que haya usado el tablero de conteo. Muéstrenle a su nueva pareja cómo contaron su colección” // “Find a partner who used a different tool to help them count their collection. If you used a 10-frame to help you count your collection, find a partner who used the counting mat. Show your new partner how you counted your collection.”
• 4 minutes: partner work time

### Activity Synthesis

• Invite at least one student who used each tool to share how they counted their collection.
• After each student shares, write or display the number and say, “Hay _____ objetos en su colección” // “There are _____ objects in their collection.”
• “¿Cómo saben que contaron cada objeto una vez?” // “How do you know that you have counted each object one time?” (I moved the objects from one side of the counting mat to the other. There are none left on this side, so I counted them all. I put them in a 10-frame and then touched and counted each one in order.)
• If needed, “Cuando contamos, un tablero de conteo o un tablero de 10 nos pueden ayudar a asegurarnos de que contamos cada objeto 1 vez” // “When we count, a counting mat or 10-frame can help us make sure that we count each object 1 time.”

## Activity 3: Centros: Momento de escoger (25 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice with addition, subtraction, and tracing numbers.

Students choose from any stage of previously introduced centers.

• Number Race
• Subtraction Towers
• 5-frames

Engagement: Provide Access by Recruiting Interest. Use visible timers or audible alerts to help students anticipate and prepare to transition between activities.
Supports accessibility for: Social-Emotional Functioning, Organization

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from:
• Number Race, Stages 1 and 2
• Subtraction Towers, Stage 1
• 5-frames, Stages 1 and 2

### Launch

• “Hoy vamos a escoger centros de los que ya conocemos” // “Today we are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Piensen qué les gustaría hacer primero” // “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.
• 10 minutes: center work time
• “Escojan qué les gustaría hacer ahora” // “Choose what you would like to do next.”
• 10 minutes: center work time

### Student Facing

Escoge un centro.

Carrera con números

Torres para restar

Tableros de 5

### Activity Synthesis

• “Mientras trabajaban en los centros hoy, ¿en qué momentos vieron a un compañero contar?” // “When did you see a classmate count during centers today?”

## Lesson Synthesis

### Lesson Synthesis

“Hemos visto diferentes formas de contar nuestras colecciones y de asegurarnos de que contamos cada objeto una vez. Cuéntenle a su pareja cómo saben si ya contaron los objetos cuando cuentan” // “We have seen different ways to count our collections and make sure that we count each object one time. Tell your partner how you keep track of the objects when you count.” (I move each object as I count it. I touch each object as I count it. I put the objects in a line and then count all of them. I move each object from one side to the other on the counting mat. I put the objects in a 10-frame and then count each one.)