# Lesson 11

Sumémosle a un número del 11 al 19

## Warm-up: Verdadero o falso: Números del 11 al 19 (10 minutes)

### Narrative

The purpose of this True or False is to elicit insights students have about composing teen numbers as a ten and some ones. This will be helpful later in the lesson when students add a single-digit number to a teen number within 20.

### 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 equation.

### Student Facing

Prepárate para explicar tu razonamiento.

• $$10 + 4 = 10 + 5$$
• $$10 + 3 = 2 + 1 + 10$$
• $$14 = 10 + 4 + 5$$

### Activity Synthesis

• “¿Alguien quiere agregar algo al razonamiento de _____?” // “Does anyone want to add on to _____ ’s reasoning?”
• “¿Decidieron si alguna de ellas era verdadera o falsa sin resolverla? ¿Cómo?” // “Did you determine if any of these were true or false without solving? How?” (I knew the first one without solving. Both had 10 + something, and one had a 4 and one had a 5, so they are not equal.)

## Activity 1: Colección de piedras (10 minutes)

### Narrative

The purpose of this activity is to elicit and discuss methods for adding a one-digit number to a teen number, within 20. Students are presented with a simple story problem type (Add To, Result Unknown) so discussion can focus on the methods students used to find the sum. Students represent and solve the problem in a way that makes sense to them (MP1). Some students may build the teen number, add counters and count all, while other students may count on from the teen number. Some students may see that the sum will still have 1 ten and just combine the ones. During the synthesis, students notice that when adding to teen numbers within 20, the unit of ten in the representation does not change—only the ones change (MP8).

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give each group access to double 10-frames and connecting cubes or two-color counters.
• “Es común que la gente coleccione piedras. La gente colecciona muchos tipos distintos de piedras. Vamos a resolver un problema sobre una colección de piedras” // “Something that is common for people to collect is rocks. People collects lots of different types of rocks. We are going to solve a problem about a rock collection.”

### Activity

• 3 minutes: independent work time
• “Compartan con su pareja cómo pensaron” // “Share your thinking with your partner.”
• 2 minutes: partner work time
• Monitor for students who represent their thinking using 10-frames to show 14 and then add 3 more.

### Student Facing

Kiran colecciona piedras.
Hasta ahora tiene 14 piedras.
Se va de excursión y recoge 3 piedras más.
¿Cuántas piedras tiene Kiran?
Muestra cómo pensaste. Usa dibujos, números o palabras.

Ecuación: ________________________________

### Activity Synthesis

• Invite previously identified students to share.
• “¿Cómo cambió la representación cuando ellos agregaron tres unidades? ¿Qué siguió siendo lo mismo?” // “How did the representation change when they added three ones? What stayed the same?” (You start with a full 10-frame and four ones, and when you add three more, that 10-frame does not change. This 10-frame changed because now there are four red counters and three yellow counters.)

## Activity 2: Escribamos ecuaciones: Suma algo más a números del 11 al 19 (10 minutes)

### Narrative

The purpose of this activity is for students to add a one-digit number to a teen number. All of the totals are within 20. Students are provided 10-frames and two-color counters which they may choose to use to represent the sums. Using 10-frames encourages students to see that the unit of ten stays the same and the ones are combined.

During the activity synthesis, the teacher records how students found the value of the sum of $$17 +2$$. It is important that the teacher write the equation the way that students think about the answer to the problem. For example, the equation $$17 + 2 = \boxed{19}$$ represents students who show 17 counters and count on as they add two more. The equation $$7 + 2 + 10 = \boxed{19}$$ or $$10+7 + 2 = \boxed{19}$$ represents students who see that the ten stays the same and they can add the ones to help them find the total.

MLR7 Compare and Connect. Synthesis: After the solutions have been presented, lead a discussion comparing, contrasting, and connecting the two equations. Ask, “¿En qué se parecen estas ecuaciones?, ¿en qué son diferentes?” // “How are these equations similar?” and “How are they different?”
Engagement: Develop Effort and Persistence. Chunk this task into more manageable parts. Check in with students to provide feedback and encouragement after each chunk.
Supports accessibility for: Attention, Social-Emotional Functioning

### Required Materials

Materials to Gather

### Launch

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

### Activity

• 5 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for students who find the value of the sum $$17 + 2$$ in these ways:
• $$17 + 2 = \boxed{19}$$
• $$7 + 2 + 10 = \boxed{19}$$

### Student Facing

En cada caso, encuentra el número que hace que la ecuación sea verdadera.
Muestra cómo pensaste. Usa dibujos, números o palabras.
1. $$12 + 5 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

2. $$6 + 11 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

3. $$\boxed{\phantom{\frac{aaai}{aaai}}} = 17 + 2$$

4. $$4 + 14 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

5. $$\boxed{\phantom{\frac{aaai}{aaai}}} = 15 + 4$$

6. $$16 + 2 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

### Activity Synthesis

• Display each missing number.
• Invite previously identified students to share.
• “¿Cómo muestra $$17 + 2 = \boxed{19}$$ el trabajo de _____?” // “How does $$17 + 2 = \boxed{19}$$ match _____’s work?” (They put 17 on and then counted 2 more—18, 19—to get the value.)
• “¿Cómo muestra $$7 + 2 + 10 = \boxed{19}$$ el trabajo de _____?” // “How does $$7 + 2 + 10 = \boxed{19}$$ match _____’s work?” (They added the ones and got 9 and then added 10 to get 19.)

## Activity 3: Centros: Momento de escoger (20 minutes)

### Narrative

The purpose of this activity is for students to choose from activities that offer practice adding and subtracting within 10. Students choose from previously introduced centers.

• Compare
• Number Puzzles
• Find the Pair

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from previous centers:
• Compare, Stage 1
• Number Puzzles, Stage 1
• Find the Pair, Stage 2

### Launch

• Groups of 2
• “Ahora van a escoger centros de los que ya conocemos” // “Now you are going to choose from centers we have already learned.”
• Display the center choices in the student book.
• “Piensen qué les gustaría hacer primero” // “Think about what you would like to do first.”
• 30 seconds: quiet think time

### Activity

• Invite students to work at the center of their choice.
• 8 minutes: center work time
• “Escojan que les gustaría hacer ahora” // “Choose what you would like to do next.”
• 8 minutes: center work time

### Student Facing

Escoge un centro.

Compara

Acertijos numéricos

Encuentra la pareja

### Activity Synthesis

• “¿Cómo deciden cuál centro será más útil para ustedes?” // “How do you choose which center will be most helpful for you?”

## Lesson Synthesis

### Lesson Synthesis

Display $$\boxed{20} = 18 + 2$$ and the double 10-frame representation.

“Hoy le sumamos números a distintos números del 11 al 19. ¿De qué formas diferentes podemos encontrar el valor que hace que la ecuación sea verdadera?” // “Today we added to teen numbers. What are different ways to find the value that makes the equation true?” (I can count up 19, 20, I can add the ones, so $$8 + 2 = 10$$ and then $$10 + 10 = 20$$, I can put 2 more in my 10-frames and see that both are filled, which is 20.)

Write equations to represent each student’s thinking.