# Lesson 11

¿Cómo lo hicieron?

## Warm-up: Verdadero o falso: Sumémosle a un número de dos dígitos (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies students have for adding within 100 using methods based on place value. As students reason about how to add the digits in the two addends, they make use of base-ten structure (MP7).

### Launch

• Display one statement.
• “Hagan una señal cuando sepan si la afirmación es verdadera o no, y puedan explicar cómo lo saben” // “Give me a signal when you know whether the statement is true and can explain how you know.”
• 1 minute: quiet think time

### Activity

• Share and record answers and strategy.
• Repeat with each statement.

### Student Facing

En cada caso, decide si la afirmación es verdadera o falsa. Prepárate para explicar tu razonamiento.

• $$24 + 3 = 54$$
• $$42 + 5 = 47$$
• $$42 + 30 = 45$$

### Activity Synthesis

• “¿Cómo pueden explicar su respuesta sin tener que encontrar el valor de ambos lados?” // “How can you explain your answer without finding the value of both sides?”

## Activity 1: ¿Cuánta basura? (15 minutes)

### Narrative

The purpose of this activity is for students to interpret equations that represent different methods for addition. When students connect the quantities in the story problem to addition equations, they reason abstractly and quantitatively (MP2). Base-ten drawings are provided for Jada and Kiran's way so that students can use the drawings and the equations to make sense of the different methods. Students compare methods that add tens and tens and ones and ones to methods that add on by place. Students may also relate the methods used by Kiran and Tyler to the make 10 methods they use when adding within 20.

This activity uses MLR8 Discussion Supports. Advances: listening, speaking

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.
• Display the image and story problem.
• “¿De qué se trata este problema?” // “What is this problem about?” (Kids who are cleaning up a park. People picking up litter.)
• “¿Qué harían para averiguar cuántas piezas de basura recogieron ellos?” // “What would you do to figure out how many pieces of litter they picked up?” (I would add 37 and 25.)
• “Jada, Kiran y Tyler averiguaron cuántas piezas de basura recogieron los estudiantes de la clase de Mai, pero lo hicieron de otra manera. Con su compañero, expliquen cómo encontró cada estudiante el valor de $$37 + 25.$$ Prepárense para explicar cómo pensaron de una forma que los demás entiendan” // “Jada, Kiran, and Tyler figure out how many pieces of litter Mai's class picked up, but they do it in different ways. With your partner, explain how each student found the value of $$37 + 25.$$ Be ready to explain your thinking in a way that others will understand.”

### Activity

• 5-7 minutes: partner work time
• Monitor for students who can explain each method:
• by connecting the drawings and the equations.
• by describing how the student thought about adding tens and ones.
• by describing how the student made a ten.

### Student Facing

Mai y sus compañeros de clase se ofrecieron como voluntarios para limpiar el parque del barrio.
Ellos recogieron 37 botellas de plástico y 25 envolturas de papel.
¿Cuántas piezas de basura recogieron en total?

Jada, Kiran y Tyler encontraron el valor de $$37 + 25$$ para averiguar cuántas piezas de basura recogieron los estudiantes de la clase de Mai.

$$37 + 25$$

$$30 + 20 = 50$$
$$7 + 5 = 12$$
$$50 + 12 = 62$$

El método de Kiran:

$$37 + 3 + 2 = 42$$
$$42 + 20 = 62$$

El método de Tyler:

$$37 + 20 = 57$$
$$57 + 3 + 2 = 62$$

### Activity Synthesis

• Invite previously identified students to share.
MLR8 Discussion Supports
• “¿Alguien puede expresar con sus propias palabras lo que compartió ____?” // “Who can restate what ____ shared in their own words?”
• 30 seconds: quiet think time
• Consider providing students time to restate what they heard to a partner before selecting one or two students to share with the class.
• Ask the original speaker if their peer was accurately able to restate their thinking.

## Activity 2: Es su turno de sumar (20 minutes)

### Narrative

The purpose of this activity is for students to find the sum of 2 two-digit numbers using one of the methods students have seen in previous activities. Students choose which method they would like to use and show their thinking using drawings, numbers or words. Although students have been analyzing base-ten drawings, if they are ready to represent their addition methods with equations, they should be encouraged to do so. Students participate in a gallery walk in which they observe the different ways the addition methods can be represented.

MLR7 Compare and Connect. Synthesis: After the Gallery Walk, lead a discussion comparing, contrasting, and connecting the different posters. 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. Check in and provide each group with feedback that encourages collaboration and community. For example, choose one of your Math Community norms to give feedback on.
Supports accessibility for: Social-Emotional Functioning, Attention

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give each group tools for creating a visual display and access to connecting cubes in towers of 10 and singles.
• “Con su compañero, encuentren el valor de $$23 + 68$$. Escojan uno de los métodos de la actividad anterior y úsenlo para encontrar el valor. Muestren cómo pensaron. Usen dibujos, números o palabras. Lleguen a un acuerdo sobre qué pasos van a usar y cómo los van a representar” // “You are going to find the value of $$23 + 68$$ with your partner. Choose one of the methods from the previous activity and work together to use it to find the value. Show your thinking using drawings, numbers, or words. Come to an agreement about the steps you will use and how you will represent them.”
• 3 minutes: partner discussion

### Activity

• “Creen una presentación visual que muestre cómo encontraron el valor de $$23 + 68$$. Incluyan dibujos y números para ayudar a los demás a entender cómo pensaron” // “Create a visual display that shows how you and your partner found the value of $$23 + 68$$. You may want to include drawings and numbers to help others understand your thinking.”
• 5-7 minutes: partner work time

### Student Facing

Encuentra el valor de $$23 + 68$$.
Muestra cómo pensaste. Usa dibujos, números o palabras.

Si te queda tiempo: Piensa en una historia matemática que se podría representar con esta expresión.
Comparte tu historia con un compañero.

### Activity Synthesis

• “Con su compañero, observen los pósteres y hablen sobre lo que observan. ¿Alguno de los pósteres muestra el método de Jada, Kiran o Tyler? ¿Cómo lo saben?” // “With your partner, look at the posters and talk about what you notice. Do any of the posters show Jada's, Kiran's, or Tyler's method? How do you know?”
• 6 minutes: gallery walk

## Lesson Synthesis

### Lesson Synthesis

“En una lección anterior, separamos cada número de dos dígitos y sumamos las decenas con las decenas y las unidades con las unidades. Hoy separamos números de dos dígitos de otras maneras. Buscamos maneras de formar una nueva decena y maneras de sumar decenas y unidades. ¿Cuál método prefieren? ¿Por qué les gusta más ese método?” // “In a previous lesson, we broke apart both two-digit numbers and added the tens and tens and ones and ones. Today we broke apart two-digit numbers in different ways. We looked for ways to make a new ten and ways to add on tens and ones. Which method do you prefer? Why do you like that method better?”

Invite students to share responses to the cool-down.