# Lesson 20

Un paseo al zoológico

## Warm-up: Conversación numérica: Usemos $10 + \boxed{\phantom{4}}$ (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding within 20.

Students may have many ideas for adding these numbers. In the synthesis, students discuss what they notice about the first two expressions. Students may notice that the expressions are equal and that one expression might help them with the other.

### 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 mentalmente el valor de cada expresión.

• $$8 + 2 + 4$$
• $$8 + 6$$
• $$7 + 3 + 6$$
• $$7 + 9$$

### Activity Synthesis

• “¿Qué observan sobre las primeras dos expresiones?” // “What do you notice about the first two expressions?” (They are both 14. If 6 was broken into 2 and 4, it would be the same expression.)

## Activity 1: ¿Cuántos reptiles? (15 minutes)

### Narrative

The purpose of this activity is for students to discuss different ways to solve a three-addend story problem in which none of the addends can be combined to make 10 without being decomposed. Students solve the problem in a way that makes sense to them. Some students may build each number separately on the 10-frames and see both are filled. Some students may manipulate the numbers and think $$8 + 7 + 5 = 8 + 2 + 5 + 5$$. Different methods for solving are highlighted in the synthesis. It is important that the teacher represents student thinking, so that these methods are visible to all.

When students make sense of the story problems and connect the quantities in the story to an equation, they reason abstractly and quantitatively (MP2).

MLR6 Three Reads. Keep books or devices closed. To launch this activity, display only the problem stem, without revealing the question. “Vamos a leer este problema-historia 3 veces” // “We are going to read this story problem 3 times.” After the 1st Read: “Cuéntenle a su pareja lo que ocurrió en la historia” // “Tell your partner what happened in the story.” After the 2nd Read: “¿Cuáles son todas las cosas de esta historia que podemos contar?” // “What are all the things we can count in this story?” Reveal the question. After the 3rd Read: “¿De qué formas diferentes podemos resolver este problema?” // “What are different ways we can solve this problem?”

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.

### Activity

• 4 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for students who:
• place 8, 7, and 5 counters on the 10-frames and see that they are both full
• count on
• represent the problem as $$8 + 2 + 5 + 5$$
• use a known sum like $$8 + 8$$ and then add 4 more.

### Student Facing

Jada fue al zoológico con su familia.
Fueron a la exhibición de reptiles y vieron 8 serpientes, 7 iguanas y 5 ranas.

¿Cuántos reptiles vio la familia de Jada?
Muestra cómo pensaste. Usa dibujos, números o palabras.

### Activity Synthesis

• Invite previously identified students to share.
• “¿Qué hicieron ellos para encontrar la suma?” // “What did they do to find the sum?”
• Record each method with an equation.

## Activity 2: Exhibiciones del zoológico (20 minutes)

### Narrative

In this activity students solve three-addend story problems within 20. Students use methods and representations that make sense to them. When students connect the quantities in the story to an equation, they reason abstractly and quantitatively (MP2). They think strategically and may either choose to use a double 10-frame or decompose and compose the numbers in a way that helps them see the sum as 10 and some ones (MP1, MP5).

Action and Expression: Internalize Executive Functions. Invite students to plan a method, including the tools they will use, for solving story problems with three addends. If time allows, invite students to share their plan with a partner before they begin.
Supports accessibility for: Organization, Attention

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.
• “Vamos a resolver problemas usando los diferentes métodos en los que hemos estado trabajando” // “We are going to solve some problems using the different methods we’ve been working on.”

### Activity

• 6–8 minutes: independent work time
• 4 minutes: partner discussion

### Student Facing

1. En la exhibición de aves, Jada vio 3 garzas, 6 halcones y 7 colibríes.
Muestra cómo pensaste. Usa dibujos, números o palabras.

2. Luego, Jada fue a la exhibición de los grandes felinos.
Había 8 leones, 4 tigres y 3 guepardos.
¿Cuántos grandes felinos había?
Muestra cómo pensaste. Usa dibujos, números o palabras.

3. Por último, Jada fue al zoológico interactivo.
Ella acarició 8 cabras, 7 ovejas y 4 cerdos.
Muestra cómo pensaste. Usa dibujos, números o palabras.

### Activity Synthesis

• Invite students to share their method for each problem.
• Record each method with an equation.

## Lesson Synthesis

### Lesson Synthesis

“En esta sección, trabajamos en diferentes formas de sumar hasta 20. ¿De qué se sienten más orgullosos? ¿Qué deben seguir practicando?” // “In this section, we worked on different ways to add within 20. What are you most proud of? What do you still need to practice?”

## Cool-down: Una visita a los primates (5 minutes)

### Cool-Down

$$4 + 8 + 6 = 10 + 8 = 18$$
$$4 + 8 = 4 + 6 + 2 = 10 + 2 = 12$$