# Lesson 14

Cientos de objetos (optional)

## Warm-up: Observa y pregúntate: Tarro de frijoles (10 minutes)

### Narrative

This warm-up prompts students to make sense of a problem before solving it, by familiarizing themselves with a context and the mathematics that might be involved. In the next activity, students will see three different ways the amount of beans in a cup are counted.

### Launch

• Groups of 2
• Display the image.
• “¿Qué observan? ¿Qué se preguntan?” // “What do you notice? What do you wonder?”
• 1 minute: quiet think time

### Activity

• “Discutan con su pareja lo que pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Share and record responses.

### Student Facing

¿Qué observas? ¿Qué te preguntas?

### Activity Synthesis

• “¿Se imaginan contar tantos frijoles? ¿Cómo lo harían?” // “Can you imagine counting out so many beans? How would you do it?”
• “Hoy vamos a seguir pensando sobre estas ideas de conteo en nuestra primera actividad” // “We are going to keep thinking about those counting ideas in our first activity today.”

## Activity 1: Taza de frijoles (10 minutes)

### Narrative

The purpose of this activity is for students to compare methods that can be used to count numbers between 100 and 999. Students see images of beans that are put in groups of 5 and another in groups of 10. A third image uses groups of 100, groups of 10, and single beans. Students make connections to place value and their understanding of the base-ten structure (MP2, MP7). They also consider opportunities for accuracy and efficiency when they articulate pros and cons for each method.

### Launch

• Groups of 2
• Display image of a cup of beans or display a cup of beans.
• Read the context aloud.

### Activity

• 1 minute: quiet think time
• 5 minutes: small-group discussion
• Monitor for students who:
• describe the organization and group sizes in each method
• describe Clare’s method in terms of hundreds, tens, and ones
• discuss ideas such as efficiency (how long it takes) and accuracy (chances of mistakes)

### Student Facing

Clare, Noah y Jada contaron una taza de frijoles. Cada uno contó 529 frijoles. Las siguientes imágenes muestran cómo contó cada uno.

La estrategia de conteo de Jada:

La estrategia de conteo de Noah:

La estrategia de conteo de Clare:

1. ¿Qué observan sobre cada estrategia?

2. ¿Qué es útil en cada estrategia?

3. ¿Qué es retador en cada estrategia?

### Activity Synthesis

• Invite previously selected students to share their observations.
• “¿Cuál de estas estrategias creen que sería la más rápida o la más lenta? Expliquen” // “Which of these strategies do you believe would be the fastest or slowest? Explain.”
• “¿Piensan que sería más fácil cometer un error usando una de estas estrategias? ¿Cuál y por qué?” // “Do you think it would be easier to make a mistake using one of these strategies? Which one and why?”
• “¿Cuál estrategia prefieren? ¿Por qué?” // “Which strategy do you prefer? Why?”

## Activity 2: Muchos frijoles (25 minutes)

### Narrative

The purpose of this activity for students to choose their own method to count between 100 and 999 objects accurately and efficiently. Students should be encouraged to use their understanding of place value.

Representation: Internalize Comprehension. Provide students with a graphic organizer, such as a sorting mat with various circles to organize the groups of beans and record how many beans are in each group.
Supports accessibility for: Organization, Memory
MLR7 Compare and Connect. Synthesis: After the Gallery Walk, lead a discussion comparing, contrasting, and connecting the different strategies used to count. To amplify student language, and illustrate connections, follow along and point to the relevant parts of the displays as students speak.

### Required Materials

Materials to Gather

### Required Preparation

• Each group of 2 to 4 students will need between one-half cup to one cup of beans or other small objects to count. If real-world objects are unavailable, centimeter cubes could be used instead.

### Launch

• Groups of 2 or 4.
• Give students each group $$\frac{1}{2}$$ to 1 cup of beans and a sticky note.
• “Van a usar el método que prefieran para contar los frijoles y después van a escribir su resultado en una nota adhesiva. Dóblenla para esconder su resultado” // “You will use any method you prefer to count the beans and then write your result on one sticky note and then fold it to hide your result.”

### Activity

• 510 minutes: small-group work time
• Monitor for students who make groups of 5, groups of 10, or groups of 100.
• Display and read the gallery walk questions.
• “Piensen sobre estas preguntas mientras caminan” // “Think about these questions as you walk around.”
• 10 minutes: gallery walk

### Student Facing

Organiza y cuenta tus frijoles. Usa el espacio para escribir cómo pensaste.

Preguntas del recorrido por el salón:

• ¿Cómo te ayuda esta estrategia a contar sus frijoles?
• ¿Cómo se puede hacer que esto sea más claro?
• ¿En qué se parece esta estrategia a tu estrategia? ¿En qué es diferente?
• ¿Tu grupo tiene más o menos frijoles? Explica tu razonamiento.

### Advancing Student Thinking

If students double count beans or groups of beans ask, “¿Cómo puedes organizar tus montones para asegurarte de no contar dos veces algunos de los montones?” // “How can you organize your piles to make sure you did not double count some of the piles?”

### Activity Synthesis

• “Cuando organizaron sus frijoles y los contaron, ¿se sintieron seguros de sus resultados? ¿Por qué?” // “When you organized your beans and counted them, did you feel confident about your results? Why?”
• Invite students to share answers to the gallery walk questions.

## Lesson Synthesis

### Lesson Synthesis

“Hoy usamos estrategias que hemos estudiado sobre los números entre 100 y 999 para contar un número grande de frijoles” // “Today, we used strategies we have been studying about numbers between 100 and 999 to count a large amount of beans.”

“¿Qué cosas importantes deben recordar cuando cuentan un número grande de objetos? ¿Qué es importante hacer cuando representan su estrategia para que sea clara para otros?” // “What are important things to remember when you count a large number of objects? What is important when you represent your strategy so that it is clear to others?”