# Lesson 10

## Warm-up: Cuántos ves: Decenas y unidades (10 minutes)

### Narrative

The purpose of this How Many Do You See is for students to subitize or use grouping strategies to describe the images they see. Students may put the tens together and the ones together, which is a method for adding that will be used later in this lesson. Students may also use the 10-frames to make a new ten in order to find the total number of counters.

### Launch

• Groups of 2
• “¿Cuántos ven? ¿Cómo lo saben?, ¿qué ven?” // “How many do you see? How do you see them?”
• Flash image.
• 30 seconds: quiet think time

### Activity

• Display image.
• “Discutan con su compañero lo que pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• Repeat for each image.

### Student Facing

¿Cuántos ves?
¿Cómo lo sabes?, ¿qué ves?

### Activity Synthesis

• “¿Alguien vio las fichas de la misma manera, pero lo explicaría de otra forma?” // “Did anyone see the counters the same way but would explain it differently?”

## Activity 1: El trabajo de Priya (10 minutes)

### Narrative

The purpose of this activity is for students to analyze a base-ten drawing used to find the value of $$37 + 26$$, in which a student adds tens and tens and ones and ones. Students make sense of the method used, and consider what made the representation of this method easy for them to understand. This will be helpful when students are asked to represent their addition methods in a way that makes sense to others.

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

Representation: Develop Language and Symbols. Make connections between the representations visible. For example, ask students to identify correspondences between the visual representation and the expression $$37 + 26$$.
Supports accessibility for: Visual-Spatial Processing, Conceptual Processing

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.

### Activity

• 2 minutes: independent work time
• “Compartan con su compañero cómo pensaron y escriban juntos una explicación de lo que Priya hizo” // “Share your thinking with your partner and work together to write an explanation of what Priya did.”
• 5 minutes: partner discussion

### Student Facing

Encuentra el valor de $$37 + 26$$.

El trabajo de Priya

¿Cómo encontró Priya el valor?

### Activity Synthesis

• Invite students to share how they interpreted Priya’s work.
• “Es muy importante representar nuestros métodos de una manera que los demás puedan entender. ¿Cómo se aseguró Priya de que los demás pudieran entender su representación?” // “Representing our methods in a way that makes sense to others is very important. How did Priya make sure her representation would make sense to others?” (She showed each number clearly. She circled the tens to show she was adding them together. She circled 10 ones to show she made a new ten. She labeled the new ten and the extra ones.)

## Activity 2: Completa el trabajo (15 minutes)

### Narrative

The purpose of this activity is for students to consider the associative and commutative properties when adding 2 two-digit numbers. In the first two problems, a base-ten drawing and an expression representing adding tens and tens or ones and ones is given as the first step. Students determine the next steps and find the sum. When students decompose the 2 two-digit numbers into tens and ones, combine the tens and ones, and then find the total, they use their place value understanding to make sense of addition (MP7).

During the activity synthesis, the teacher records students’ thinking using premade posters of 34 and 57 as tens and ones. Students discuss that you can add the parts of the numbers in any order.

MLR2 Collect and Display. Circulate, listen for and collect the language students use as they work with a partner. On a visible display, record words and phrases such as: “Primero, . . .”, “Después, . . .”, “decenas”, “unidades”, “suma” // “First, . . . ,” “Next, . . . ,” “tens,” “ones,” “sum.” Invite students to borrow language from the display as needed, and update it throughout the lesson.

### Required Preparation

• Create two separate posters that show base-ten drawings of 34 and 57. Leave space to write equations underneath the drawings.

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.
• 4 minutes: partner work time
• “¿En qué se diferencian las formas en las que encontraron los valores de $$28 + 56$$$$27 + 44$$?” // “What is the difference between how you solved $$28 + 56$$ and $$27 + 44$$.” (For $$28 + 56$$, I added the tens first, then the ones. For $$27 + 44$$ I added the ones first, then the tens.)
• 1 minute: partner discussion
• Share responses.

### Activity

• 4 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for a student who starts by adding the tens and a student who starts by adding the ones for $$34 + 57$$.

### Student Facing

1. En cada caso se muestra una expresión que sirve como primer paso para encontrar el número que hace que la ecuación sea verdadera.
En cada caso, completa el trabajo para encontrar el número que hace que la ecuación sea verdadera.
Muestra cómo pensaste. Usa dibujos, números o palabras.

1. $$28 + 56=\boxed{\phantom{\frac{aaai}{aaai}}}$$

Primer paso: $$20 + 50$$

2. $$27 + 44=\boxed{\phantom{\frac{aaai}{aaai}}}$$

Primer paso: $$7 + 4$$

2. Encuentra el valor de cada suma.
Muestra cómo pensaste. Usa dibujos, números o palabras.

1. $$34 + 57$$
2. $$18 + 55$$

### Activity Synthesis

• Invite previously identified students to share.
• Use the prepared posters to represent each student’s thinking.
• “¿En qué se parecen estos métodos? ¿En qué son diferentes?” // “How are these methods the same? How are they different?” (They both add tens and tens and ones and ones. One person added ones first and the other added tens first. They got the same answer whether they added tens first or ones first.)
• “¿Por qué ambos funcionan?” // “Why do they both work?” (You can add in any order and you still get the same number.)

## Activity 3: Conozcamos: “Acertijos numéricos: Hasta 100 componiendo” (15 minutes)

### Narrative

The purpose of this activity is for students to learn stage 4 of the Number Puzzles center. Students work together to use digit cards to make addition equations within 100 with composing a ten. Each digit card may only be used one time on a page.

### Required Materials

Materials to Gather

Materials to Copy

• Number Puzzles Addition Stage 4 Gameboard, Spanish

### Required Preparation

• Each group of 2 needs a set of digit cards from the previous center, Number Puzzles.

### Launch

• Groups of 2
• Give each group a set of cards and gameboards.
• “Estos acertijos numéricos tienen ecuaciones de suma con números de dos dígitos. Usen las tarjetas de dígitos para hacer que cada ecuación sea verdadera. Recuerden que pueden usar cada tarjeta solo una vez en cada página” // “These number puzzles have addition equations with two-digit numbers. Use the digit cards to make each equation true. Remember that you can only use each card once on a page.”

### Activity

• 10 minutes: partner work time

### Activity Synthesis

• Display a gameboard.
• “¿Cuál ecuación pueden completar primero?” // “Which equation can you fill in first?”

## Lesson Synthesis

### Lesson Synthesis

Display posters from the Activity 2 synthesis.

“Hoy sumamos decenas con decenas y unidades con unidades. Nos dimos cuenta de que podemos sumar primero las unidades o primero las decenas. ¿Qué prefieren sumar primero: las unidades o las decenas? ¿Por qué les gusta más ese método?” // “Today we added tens and tens and ones and ones and saw that we can add the ones first or the tens first. Do you prefer to add the ones first or the tens first? Why do you like that method better?” (I like to add the tens first because they come first in the number. I like to add the ones first because I like to add numbers that make a new ten.)