# Lesson 5

Formemos una decena

## Warm-up: Cuántos ves: Muchos tableros de 10 (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. The images include 10-frames to elicit students' work when adding within 20 and encourage students to think about composing a ten by counting on, which will be the focus of activities later in the lesson.

### Launch

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

### Activity

• Display the image.
• “Discutan con su pareja 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

• “¿En qué se parecen y en qué son diferentes la segunda y la tercera imagen?” // “How are the second and third images the same and different?” (In the third image all of the 10-frames are full, but in the second they are not.)

## Activity 1: Escojamos una manera de sumar (20 minutes)

### Narrative

The purpose of this activity is for students to add a one-digit number and a two-digit number in a way that makes sense to them. As students add, they may apply their learning from previous lessons to count on, make a new ten, apply the commutative property, or add ones and ones.

Monitor and select students who use the following methods to share in the synthesis:

• Start with 47, count on 8 ($$47 + 8$$)
• Start with 47 and decompose the 8 into 3 and 5 to make a new ten ($$47 + 3 + 5$$)
• Add the ones ($$7 + 8$$), then add on the tens ($$15 + 40$$)

In addition to these different methods, monitor for different ways that students represent their thinking (connecting cubes, drawings, equations). Students who use connecting cubes or base-ten drawings may physically compose a new unit of ten. This representation will be explored further in future lessons, but can also be used in this activity synthesis when sharing methods that show adding the ones, then adding the tens.

Action and Expression: Internalize Executive Functions. Invite students to plan a method, including the tools they will use, for finding the sum. If time allows, invite students to share their plan with a partner before they begin.
Supports accessibility for: Organization, Conceptual Processing, Language

### Launch

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

### Activity

• 3–5 minutes: independent work time
• “Discutan con su compañero cómo pensaron” // “Share your thinking with your partner.”
• 3 minutes: partner discussion
• As students work, consider asking:
• “¿Dónde está el 47 en su representación?” // “Where is the 47 in your representation?”
• “¿Dónde está el 8 en su representación?” // “Where is the 8 in your representation?”
• “¿Cómo encontraron la suma?” // “How did you determine the sum?”

### Student Facing

Encuentra el valor de $$8 + 47$$.
Muestra cómo pensaste. Usa dibujos, números o palabras.

### Advancing Student Thinking

If students count on to find the sum, consider asking:

• “¿Cómo encontraste la suma?” // “How did you find the sum?”
• “¿Cómo podrías usar tableros de 10 o cubos encajables para encontrar la suma sin contar de uno en uno?” // “How could you use 10-frames or connecting cubes to find the sum without counting by one?”

### Activity Synthesis

• Invite previously identified students to share in the order listed in the activity narrative. If students only share equations, represent their thinking with connecting cubes or base-ten drawings.
• “¿En qué se parecen las maneras en las que los estudiantes encontraron la suma? ¿En qué son diferentes?” // “What is the same about how each student found the sum? What is different?” (They all got 55. The first one started at 47 and counted on by ones. The second one added 3 to 47 to make 50 then added the 5 ones. The last one added the ones first then added the tens.)

## Activity 2: Súmalas, compañero (20 minutes)

### Narrative

The purpose of this activity is for students to practice adding a one-digit number and a two-digit number in a way that makes sense to them. Students may choose to use methods shared in the previous activity. Give half of the class one-digit numbers and the other half two-digit numbers. Students pair up to create a sum with a two-digit number and a one-digit number. In some problems, the sum will require composing a ten when adding ones to ones. Monitor for students who share ways they make a new ten with connecting cubes or drawings to share in the synthesis.

When students choose a method to add based on the pair of numbers they are adding, they make use of structure and apply regularity in reasoning (MP7, MP8). This could mean counting on when the 1-digit number is small, adding the ones when there is no new ten, and adding on to make a ten if needed.

MLR8 Discussion Supports. Synthesis: For each method that is shared, invite students to turn to a partner and restate what they heard using precise mathematical language.

### Required Materials

Materials to Gather

Materials to Copy

• Add Em' Up Cards (2-digit and 1-digit numbers to 100)

### Required Preparation

• Create a set of cards from the blackline master for the class.

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.
• Give half of the students one-digit number cards and half of the students two-digit number cards.
• Display the student workbook page with the practice round.
• “Cada persona tiene una tarjeta con un número. Ustedes van a buscar un compañero y van a encontrar la suma de sus dos números. Un estudiante debe tener un número de un dígito y el otro debe tener un número de dos dígitos. Juguemos una ronda juntos” // “Each person has a card with a number on it. You will find a partner and find the sum of your two numbers. One student should have a one-digit number and the other should have a two-digit number. Let's do one round together.”
• Invite one student with each kind of card to share their number.
• “Encuentren la suma de los números. Muestren cómo pensaron. Usen dibujos, números o palabras. Después, escriban una ecuación que muestre el valor que encontraron” // “Find the sum of the numbers. Show your thinking using drawings, numbers, or words. Then write an equation that shows the value you found.”
• 2 minutes: independent work time
•  Share an equation that could be used.
• “Ahora todos vamos a jugar unas rondas” // “Now we will all play a few rounds.”

### Activity

• “Busquen un compañero y encuentren la suma de sus números” // “Find a partner and find the sum of your numbers.”
• 5 minutes: partner work time
• “Intercambien tarjetas con su compañero y busquen un nuevo compañero” // “Switch cards with your partner and find a new partner.”
• Repeat as time allows.
• Monitor for students whose sum:
• does not require composing a new ten.
• requires composing a new ten when adding ones and ones.

### Student Facing

Ronda de práctica:
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: __________________________________

Ronda 1:
Muestra cómo pensaste. Usa dibujos, números o palabras

Ecuación: __________________________________

Ronda 2:
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: __________________________________

Ronda 3:
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: __________________________________

Ronda 4:
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: __________________________________

Ronda 5:
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: __________________________________

### Activity Synthesis

• Invite previously identified students to share.
• After each student shares, ask “¿Por qué escogiste este método?” // “Why did you choose this method?” (Since I was adding only 3, I could count on quickly. The number 9 would take too long to count on so I broke it apart to make a new ten and then added the rest.)

## Activity 3: El profesor de Tyler [OPTIONAL] (15 minutes)

### Narrative

The purpose of this activity is for students to solve story problems that require adding a two-digit number and a one-digit number with composing a ten. This activity offers additional practice using methods discussed in the previous activities, while giving context for adding these quantities. Students share different times in their lives that they have added or seen others add quantities like those they have been adding. This activity is optional because it provides practice solving story problems with numbers larger than 20, which is not an expectation of students in grade 1.

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.
• Read the first problem aloud.
• “¿De qué se trata la historia? ¿Cómo podemos descifrar cuánto dinero recolectó el profesor de Tyler?” // “What is this story about? How can we find out how much money Tyler’s teacher collected?” (It is about money for a field trip. We can add $$37 + 7$$.)

### Activity

• “Resuelve el problema para encontrar cuánto dinero recolectó el profesor de Tyler. Después, resuelve el siguiente problema” // “Solve the problem to find out how much money Tyler’s teacher collected. Then solve the next problem.”
• 3 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for students who use connecting cubes or base-ten drawings to solve.

### Student Facing

1. El profesor de Tyler recolectó 37 dólares para la excursión de la clase.
Después, alguien trajo 7 dólares más.
¿Cuánto dinero recolectó el profesor de Tyler?
Muestra cómo pensaste. Usa dibujos, números o palabras.

2. El profesor de Tyler necesita saber si todos sus estudiantes están en el salón.
Hay 8 estudiantes sentados en las mesas y 26 estudiantes están en la alfombra.
¿Cuántos estudiantes hay en el salón?
Muestra cómo pensaste. Usa dibujos, números o palabras.

### Activity Synthesis

• Invite previously identified students to share their method for each problem.

## Lesson Synthesis

### Lesson Synthesis

Display $$45 + 3=48$$ and $$45 + 8=53.$$

“¿Qué observan sobre estas ecuaciones?” // “What do you notice about these equations?” (Both equations start with 45. One equation shows the sum is 48 and the other shows the sum is 53. The first equation shows 4 tens and some ones on both sides. The other equation shows 4 tens and some ones on one side and 5 tens and some ones on the other side.)

“Cuando sumamos un número de dos dígitos y un número de un dígito, a veces la suma tiene el mismo número de decenas que el número de dos dígitos con el que empezamos. Por ejemplo, en esta ecuación, 48 tiene el mismo número de decenas que 45. Algunas veces, la suma tiene más decenas que el número de dos dígitos. Por ejemplo, en esta ecuación, 53 tiene más decenas que 45. ¿Por qué creen que esto pasa?” // “Sometimes when adding two-digit and one-digit numbers the sum has the same number of tens as the two-digit number you start with, like 48 has the same number of tens as 45 in this equation. Sometimes the sum has more tens than the two-digit number, like 53 has more tens than 45 in this equation. Why do you think that happens?” (Sometimes when you count on, you count to the next ten. When you have more than ten ones, you make a new ten, so the value shows more tens.)