# Lesson 2

Asociemos representaciones de decenas

## Warm-up: Exploración de estimación: Cubos y torres (10 minutes)

### Narrative

The purpose of an Estimation Exploration is to practice the skill of estimating a reasonable answer based on experience and known information. When students notice that they can make a more accurate estimate more readily when the connecting cubes are grouped in towers of 10 they make use of base-ten structure (MP7).

This is the first time students participate in this routine in grade 1. The teacher can begin by saying, “Hoy vamos a hacer un nuevo calentamiento que se llama ‘Exploración de estimación’. En esta actividad vamos a ver una colección de objetos. Su tarea es mirar una imagen y pensar sobre cuántos objetos hay” // “Today we are doing a new warm-up called Estimation Exploration. In this activity we are going to see a collection of objects. Your job is to look at the image and think about how many objects there are.” Let students know that they should estimate, or find a value that is close to the correct value, without counting each one. As needed, clarify that the number they come up with is called an estimate.

### Launch

• Groups of 2
• Display the first image.
• “¿Qué estimación sería muy alta?, ¿muy baja?, ¿razonable?” //  “What is an estimate that’s too high?” “Too low?” “About right?”
• 1 minute: quiet think time

### Activity

• “Discutan con su compañero cómo pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• “Miremos otra imagen de la misma colección” // “Let’s look at another image of the same collection.”
• Display the second image.
• “Teniendo en cuenta la segunda imagen, ¿quieren ajustar o cambiar sus estimaciones?” // “Based on the second image, do you want to revise or change your estimates?”

### Student Facing

Ronda 1: ¿Cuántos cubos?

Escribe una estimación que sea:

muy baja razonable muy alta
$$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$

Ronda 2: ¿Cuántos cubos hay?

Escribe una estimación que sea:

muy baja razonable muy alta
$$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$

### Activity Synthesis

• “Miremos nuestras estimaciones ajustadas. ¿Por qué las estimaciones fueron más precisas la segunda vez?” // “Let’s look at our revised estimates. Why were these estimates more accurate the second time?” (Some of the cubes are organized. We could see there were more than 2 tens.)
• “Hay 30 cubos” // “There are 30 cubes.”

## Activity 1: Representaciones de decenas (20 minutes)

### Narrative

The purpose of this activity is for students to make connections between representations of multiples of 10. Students match cards that show multiples of 10 with pictures, numbers, and words. Each student is given a card and then moves around the room to find the other two students whose cards have the same value.

During the synthesis, the teacher and students create a chart to display the matches. Students discuss the direct connection between the number, the written number of tens, and the representation of towers of 10. When students notice and describe that the first digit in each number matches the written number of tens and the number of towers of 10, they look for and make sense of the base-ten structure (MP7).

Engagement: Develop Effort and Persistence. Differentiate the degree of difficulty or complexity. Some students may benefit from starting with more accessible values. For example, cards with a value of 10 or 20.
Supports accessibility for: Social-Emotional Functioning, Visual-Spatial Processing

### Required Materials

Materials to Copy

• Representations of Tens, Spanish

### Required Preparation

• Create a set of cards from the blackline master for the class. Each student will only need one card.
• Create a large chart titled “Representations of Tens” at the top. Draw three columns. Label columns “Number,” “Number of Tens,” and “Drawing.”

### Launch

• Groups of 2
• Give each student a card.
• “Hoy vamos a jugar un juego en el que van a buscar tarjetas que correspondan” // “Today you will play a game in which you try to find cards that match.”
• “Para jugar este juego, cada uno recibirá una tarjeta. Encuentren a los otros dos estudiantes que tengan tarjetas con el mismo valor. Cada vez que comparen tarjetas con otro estudiante, discutan si sus tarjetas tienen o no el mismo valor y cómo lo saben” // “To play this game, each of you will get one card. Find the other two students who have cards with the same value. Each time you compare cards with another student, discuss whether or not your cards have the same value and how you know.”

### Activity

• 5 minutes: partner work time
• If time: Shuffle the cards and have students repeat the activity with new groups.
• As students work, consider asking
• “¿Cómo saben que estas tarjetas corresponden?” // “How do you know these cards match?”
• “¿Cuántas decenas tiene esta tarjeta?” // “How many tens does this card have?”

### Activity Synthesis

• “Examinemos las correspondencias que vimos hoy durante el juego” // “Let’s look at the matches we saw during the game today.”
• Write 10 in the first column of the chart.
• “¿Quién tiene 10? ¿Cómo lo saben?” // “Who has 10? How do you know?”
• Repeat for all multiples of 10, discussing how students know their cards match for each multiple of 10.

## Activity 2: ¡Coinciden! (15 minutes)

### Narrative

The purpose of this activity is for students to connect written multiples of 10 to base-ten representations. Students notice a connection between how the numbers are said, written, and represented with tens. For example, “70” has the word “seven” as it is said, the digit “7” when it is written, and is represented with seven tens. Each number name is written under the number in this activity. Students are not expected to spell number names.

MLR8 Discussion Supports. Invite students to begin partner interactions by repeating the question, “¿Cómo emparejaron las torres de 10 con los números escritos?” // “How did you match the towers of 10 to the written numbers?” This gives both students an opportunity to produce language.

### Required Materials

Materials to Gather

Materials to Copy

• It's a Match (10-90) words, numbers, pictures, Spanish

### Launch

• Groups of 2
• Give each student a blackline master and access to connecting cubes.

### Activity

• 5 minutes: independent work time
• 3 minutes: partner discussion
• Monitor for students who count the number of towers, match correctly, and can explain how they knew.

### Activity Synthesis

• Invite previously identified students to share.
• “¿Cómo supieron cuáles representaciones correspondían?” // “How did you know which representations matched?” (I counted by ten and found the number. I said 10, 20, 30, 40, 50, and found 50.)

## Lesson Synthesis

### Lesson Synthesis

“Hoy pensamos sobre cómo contar cosas que están organizadas en grupos de 10 y examinamos los números que las representan” // “Today we thought about how to count things that are arranged in groups of 10 and looked at the numbers that represent them.”

Display one row of the chart made during the activity 1 synthesis; for example: 30, 3 towers of 10, 3 tens
“¿Qué observan sobre las torres de 10 y el número que las representa?” // “What do you notice about the towers of 10 and the number that represents them?” (30 has a 3 in it, there are 3 towers of 10 or 3 tens.)
“El 3 en el número 30 nos dice cuántas decenas hay” // “The 3 in the number 30 tells us how many tens there are.”

Display another row on the chart.
“¿Cuántas torres hay?” // “How many towers are there?” (7)
“¿Cuántas decenas hay?” // “How many tens are there?” (7 tens because each tower is 10.)Displayed math (span)
“¿Cuántos cubos hay?” // “How many cubes are there?” (70)