# Lesson 13

Resolvamos problemas de grupos iguales

## Warm-up: Exploración de estimación: Multipliquemos números del 11 al 19 (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.

### Launch

• Groups of 2
• Display the expression.
• “¿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 pareja cómo pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.

### Student Facing

$$4 \times 18$$

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

• “¿Alguien tiene una estimación menor que ___? ¿Alguien tiene una estimación mayor que ___?” // “Is anyone’s estimate less than ___? Is anyone’s estimate greater than ___?”
• “Teniendo en cuenta esta discusión, ¿alguien quiere ajustar su estimación?” // “Based on this discussion does anyone want to revise their estimate?”

## Activity 1: Problemas con números del 11 al 19 (20 minutes)

### Narrative

The purpose of this activity is for students to work with problems that involve multiplication within 100 where one factor is a teen number. This is the first time students have worked with problems with numbers in this range, so they should be encouraged to use the tools provided to them during the lesson if they choose (MP5). Students should also be encouraged to use strategies and representations from the previous section. As students are paired to create posters for the next activity, try to include a variety of approaches for students to see during the gallery walk in the next activity such as:

• Counting by the teen number.
• Counting by the single digit number.
• Use the distributive property to decompose the teen number to multiply in parts.
• Use the distributive property and place value understanding to decompose the teen number into tens and ones to multiply in parts.

### Required Materials

Materials to Gather

Materials to Copy

• Centimeter Grid Paper - Standard

### Launch

• Groups of 2
• “Por turnos, discutan con su compañero en qué se parece y en qué se diferencia el primer problema de los problemas que vieron antes” // “Turn and talk to your partner about how the first problem is the same and different than problems you’ve seen before.” (It involves equal groups. It's about a farmers market. It’s asking for the total number of something. It uses the word dozen instead of saying the number.)
• 1–2 minutes: partner discussion
• If needed clarify that a dozen is 12 and refer students to the illustration of a dozen eggs.
• Give students access to connecting cubes or counters, grid paper, and base-ten blocks.

### Activity

• “Resuelvan estos problemas y muestren cómo pensaron. Usen objetos, dibujos o un diagrama” // “Solve these problems and show your thinking using objects, a drawing, or a diagram.”
• 6–8 minutes: independent work time
• As students work, consider asking:
• “¿Qué estrategias que han usado antes pueden intentar aquí?” // “What strategies have you used before that you could try here?”
• “¿Cómo podrían representar sus ideas sobre el problema?” // “How can you represent your thinking about the problem?”
• “¿En qué parte de su trabajo pueden ver _____?” // “Where can you see _____ in your work?”
• Monitor for students who solve the second problem in the same way to pair to create a poster together. Try to include a variety of approaches.
• “Ahora van a hacer un póster que muestre cómo pensaron en el segundo problema. Trabajen con un compañero que haya resuelto el problema de la misma forma que ustedes” // “Now you are going to create a poster to show your thinking on the second problem with a partner who solved the problem in the same way you did.”
• Give each group tools for creating a visual display.
• 6–8 minutes: partner work time

### Student Facing

Resuelve cada problema. Muestra cómo pensaste. Usa objetos, dibujos o un diagrama.

1. Un vendedor de un mercado agrícola tiene 7 docenas de huevos al finalizar el día. ¿Cuántos huevos tiene el vendedor?
2. En el mercado agrícola hay un espacio para que los artistas toquen su música. El sitio tiene algunas sillas para que las personas se sienten a escucharlos. Hay 5 filas de sillas y cada fila tiene 15 sillas. ¿Cuántas sillas hay?
3. En un puesto de un mercado agrícola hay una mesa. Los lados de la parte de arriba de la mesa miden 4 pies y 6 pies. ¿Cuál es el área de la parte de arriba de la mesa?

### Student Response

If students say they aren't sure how to start the problem, consider asking:

• “¿De qué se trata el problema?” // “What is the problem about?”
• “¿Cómo podrías usar bloques en base diez o papel cuadriculado para ayudarte a resolver el problema?” // “How could you use base-ten blocks or grid paper to help you solve the problem?”

### Activity Synthesis

• Display posters around the room.

## Activity 2: Recorrido por el salón: Problemas con números del 11 al 19 (15 minutes)

### Narrative

The purpose of this activity is for students to consider what is the same and what is different about the ways that students solved problems involving multiplication of a teen number. Students may notice representations that were used, as well as different strategies that were used to find the total in the problem. The important thing is that students see a variety of ways to represent and solve the problem.

MLR7 Compare and Connect. Synthesis: After the Gallery Walk, lead a discussion comparing, contrasting, and connecting the different representations. “¿Cómo se ve el número de sillas en cada método? ¿Por qué al usar distintas estrategias obtuvimos el mismo resultado?” // “How did the number of chairs show up in each method? Why did the different approaches lead to the same outcome?” To amplify student language, and illustrate connections, follow along and point to the relevant parts of the displays as students speak.
Engagement: Develop Effort and Persistence. Invite students to generate a list of shared expectations for group work. Record responses on a display and keep visible during the activity.
Supports accessibility for: Social-Emotional Functioning

### Launch

• Groups of 2
• “Antes de que comiencen el recorrido por el salón, ¿qué cosas pueden buscar mientras observan el trabajo de los demás estudiantes?” // “Before you begin the gallery walk, what are some things you could look for as you look at other students’ work?” (Ways they showed their thinking. How they found the solution to the problem.)
• Share responses.

### Activity

• “Visiten los pósteres. Discutan con su compañero en qué se parecen y en qué son diferentes las ideas de los pósteres” // “Visit the posters. Discuss with your partner what is the same and what is different about the thinking on each poster.”
• 8–10 minutes: gallery walk

### Student Facing

Mientras visitas los pósteres con tu compañero, discutan en qué se parecen y en qué son diferentes las ideas que se muestran en los pósteres.

### Activity Synthesis

• Give students a chance to ask questions they have about any posters.
• “¿En qué se parecen las ideas que se muestran en los pósteres?” // “What is the same about the thinking shown on the posters?”
• “¿En qué son diferentes las ideas que se muestran en los pósteres?” // “What is different about the thinking shown on the posters?”

## Lesson Synthesis

### Lesson Synthesis

“Hoy resolvimos algunos problemas en los que había multiplicación con números del 11 al 19. ¿Qué estrategias o representaciones vieron hoy que les gustaría intentar en el futuro?” // “Today we solved some problems that involved multiplying teen numbers. What were some strategies or representations you saw today that you’d like to try in the future?” (One of the posters that I saw used groups of 5 to find the total. One of the groups broke the teen number into tens and ones. One group used a grid to represent the problem. One of the groups used base-ten blocks to represent the problem.)

“¿Cómo les ayudó el trabajo que hicieron multiplicando números más pequeños a multiplicar números del 11 al 19?” // “How did your work multiplying smaller numbers help you multiply teen numbers?” (I broke the teen numbers apart like I did with smaller numbers that are challenging to multiply.)