# Lesson 9

Suma con una decena

## Warm-up: Observa y pregúntate: Números del 11 al 19 (10 minutes)

### Narrative

The purpose of this warm-up is to elicit the idea that teen numbers can be represented with different tools, which will be useful when students build teen numbers on 10-frames in a later activity. While students may notice and wonder many things about these images, seeing the tower of 10 and the full 10-frame as a unit is an important discussion point.

### 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

• “¿Cómo descifraron cuántos objetos hay en cada imagen?” // “How could you figure out how many objects there are in each image?” (I saw that one whole 10-frame was filled, so I knew that was 10. Then I counted on. I saw that the connecting cubes were in a tower of 10 and then there were some more left over. I could count all the objects in the image.)

## Activity 1: Hagámoslo: Números del 11 al 19 y tableros de 10 (20 minutes)

### Narrative

The purpose of this activity is for students to continue to explore teen numbers as 1 ten and some ones, using a new version of a familiar tool, the double 10-frame. Students choose a teen number and build it. As they build teen numbers, students should notice that every teen number has a completed 10-frame. or 1 ten, in common. This further solidifies student understanding that all teen numbers have 1 ten. Some students may build the teen number, counter by counter, each time. These students are still developing an understanding of 10 ones as 1 ten. Some students may realize that one of the 10-frames is always completely filled and only change the ones. When students notice the relationship between teen numbers and the 10 + n pattern, they look for and make use of structure (MP7). Students who leave one 10-frame full and change the counters in the other 10-frame are observing regularity in how the teen numbers are formed (MP8).

Double 10-Frames are provided as a blackline master. Students will continue to use these throughout the year. Consider copying them on cardstock or laminating them and keeping them organized to be used repeatedly.

MLR8 Discussion Supports. Invite students to begin partner interactions by repeating the question, “¿Cómo podemos usar fichas y un tablero de 10 para construir este número?” // “How can we use a ten-frame and counters to build this number?” This gives both students an opportunity to produce language.

### Required Materials

Materials to Gather

Materials to Copy

• Number Cards 11-20
• Double 10-Frame - Standard

### Required Preparation

• Create a set of Number Cards (11-20)  from the blackline master for each group of 2.

### Launch

• Groups of 2
• Give each group a set of cards, a double 10-frame, and access to at least 20 connecting cubes or two-color counters.
• “Hoy vamos a usar nuestros tableros de 10 dobles para construir números del 11 al 19. Hagamos uno juntos” // “We’re going to use our double 10-frames to build teen numbers today. Let's do one together.”
• Choose a card.
• “¿Qué número tiene mi tarjeta? Construyamos ese número en el tablero de 10 doble” // “What number is on my card? Let's build that number on the double 10-frame.”
• Demonstrate building the teen number.
• “Ahora escribamos una ecuación para mostrar cómo construimos el número” // “Now we write an equation to show how we built the number.”
• Write an equation such as 10 + 4 = 14.

### Activity

• “Ahora van a construir más números del 11 al 19 con su compañero. Asegúrense de que ambos estén de acuerdo en cómo construir el número y en qué ecuación escribir” // “Now you will build more teen numbers with your partner. Make sure you both agree on how to build the number and what equation to write.”
• 10 minutes: partner work time
• Monitor for students who:
• build a new ten each time
• count the 10 each time
• change the ones only

### Student Facing

Usa tus tableros de 10 para construir números del 11 al 19.
Escribe una ecuación que muestre el número que construiste.

número del 11 al 19 ecuación

Si tienes tiempo, escribe otra ecuación para cada uno de los números del 11 al 19.

### Student Response

If students remove all counters from the 10-frames and build a new ten for each teen number, consider asking:

• “¿Puedes explicar cómo construiste este número?” // “Can you explain how you built this number?”
• “¿Puedes dejar algunas de las fichas aquí como ayuda para construir tu siguiente número?” // “Can you keep some of the counters here to help you build your next number?”

### Activity Synthesis

• “Al construir estos números, ¿qué parte de la ecuación era la misma? ¿Qué parte era diferente?” // “When you were building these numbers, what part of the equation was the same? What part was different?” (There was always 10 in each equation. I was adding each time. The total changed and was always a teen number. The number I was adding to 10 changed.)

## Activity 2: Ecuaciones con una decena (15 minutes)

### Narrative

The purpose of this activity is for students to determine the value that makes addition equations true. The numbers in the equations all use the relationship between 1 ten and some ones and teen numbers. Students find the value that makes the equation true with one addend or the total unknown. This will help when students solve story problems with the unknown value in different positions in a later lesson.

Representation: Internalize Comprehension. Activate background knowledge. Begin by asking, “¿Estos problemas les recuerdan algo que hayamos visto o hecho antes?” // “Do these problems remind anyone of something we have seen or done before?”
Supports accessibility for: Conceptual Processing, Attention

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give students access to double 10-frames and connecting cubes or two-color counters.

### Activity

• 6 minutes: independent work time
• 4 minutes: partner discussion

### Student Facing

En cada caso, encuentra el número que hace que la ecuación sea verdadera.
Muestra cómo pensaste. Usa dibujos, números o palabras.

1. $$14 = 10 + \boxed{\phantom{\frac{aaai}{aaai}}}$$
2. $$10 + 5 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
3. $$16 = \boxed{\phantom{\frac{aaai}{aaai}}} + 6$$
4. $$10 + \boxed{\phantom{\frac{aaai}{aaai}}} = 12$$
5. $$\boxed{\phantom{\frac{aaai}{aaai}}}+ 3 = 13$$
6. $$13 = \boxed{\phantom{\frac{aaai}{aaai}}} + 10$$

### Activity Synthesis

• “¿Cómo se relacionan los dos últimos problemas?” // “How are the last two problems related?” (They both show that 13 is the same as 10 and 3. 13 is the sum but they have different missing values.)

## Lesson Synthesis

### Lesson Synthesis

Display 18 using double 10-frames.

“Hoy mostramos números del 11 al 19 en tableros de 10 dobles y escribimos ecuaciones para representarlos. ¿Qué ecuaciones pueden escribir para representar este número?” // “Today we showed teen numbers on double 10-frames and wrote equations to match. What equations can you write to represent this number?” ($$10 + 8 = 18$$, $$18 = 8 + 10$$)

“¿Cómo nos ayudan estas ecuaciones a entender los números del 11 al 19?” // “How do these equations help you understand teen numbers?” (Teen numbers can be made up of a ten and some number of ones. This can be represented as 10 plus something.)