# Lesson 18

1 más o 1 menos con torres y números

## Warm-up: Actuémoslo: Tenedores para la cena (10 minutes)

### Narrative

The purpose of this warm-up is to allow students to connect language to mathematical representation, which will be useful when students need to represent and compare quantities in a later activity. This warm-up gives students opportunities to make sense of a problem by acting it out first before thinking about how to solve the problem (MP1).

### Launch

• Groups of 2
• Display and read the story.
• “¿De qué se trata la historia?” // “What is the story about?”
• 30 seconds: quiet think time
• Share responses.
• “¿Cómo pueden actuar esta historia?” // “How can you act out this story?”
• 30 seconds: quiet think time

### Activity

• “Discutan con su pareja cómo pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Share responses.
• Choose a way to represent the story as a class.

### Student Facing

Mai está ayudando a repartir los tenedores para la cena.
Hay 9 personas sentadas en la mesa.
Mai tiene 7 tenedores.
¿Hay suficientes tenedores para que cada persona reciba uno?

### Activity Synthesis

• “¿Hay suficientes tenedores para que cada persona reciba uno? ¿Cómo lo saben?” // “Are there enough forks for each person to get one? How do you know?” (There are not enough forks for each person to get one. When we acted out the story, some of the people didn’t get forks.)

## Activity 1: ¿Qué falta? (10 minutes)

### Narrative

The purpose of this activity is for students to determine the missing number and tower from the set of 1–10. Students may use the written numbers or the towers to determine which are missing. Students may begin counting from 1 to find the missing number or tower. Students may create a cube tower with the same number of cubes as the tower next to the missing tower, and put 1 more cube on or take 1 cube away. Students may use the existing numbers and determine which number is more or less (“6 is 1 more than 5. 6 is 1 less than 7.”) In the synthesis, students will discuss how they thought about 1 more or 1 less to find the missing number. When students relate the count sequence, via cube towers or numbers, to 1 more and 1 less they are using a vital structure of the count sequence (MP7).

### Required Materials

Materials to Gather

### Required Preparation

• Each group of 2 needs cube towers of 1–10 and number cards 1-10.

### Launch

• Groups of 2
• Give each group access to number cards and cube towers 1–10.
• “Pongan sus torres y números en orden del 1 al 10. Pongan el número debajo de cada torre” // “Put your towers and numbers in order from 1–10. Put the number under each tower.”
• 1 minute: partner work time
• “Ahora una persona va a cerrar los ojos. Su pareja va a quitar una torre y el número que le corresponde y lo va a esconder detrás de su espalda” // “Now one person will close their eyes and their partner will remove one tower and the number that matches and hide them behind their back.”
• Demonstrate by telling the whole class to close their eyes. Remove the tower and number card that show 4.
• “Abran sus ojos. ¿Cuál número y cuál torre faltan? ¿Cómo lo saben?” // “Open your eyes. Which number and tower are missing? How do you know?”
• 30 seconds: quiet think time.
• 30 seconds: partner discussion
• “Faltaban el número y la torre que muestran 4” // “The number and tower that show 4 were missing.”
• Show the tower and the number card that was hidden.
• “Sigan jugando por turnos con su pareja” // “Continue playing, taking turns with your partner.”

### Activity

• 5 minutes: partner work time
• Monitor for groups using 1 more or 1 less to determine the missing number.

### Student Response

If students do not use the towers or numbers to identify what is missing, consider asking:

• “¿Qué estás intentando descubrir?” // “What are you trying to figure out?”
• “¿Puedes construir una torre que vaya en este lugar?” // “Could you build a tower that fits in this spot?”

### Activity Synthesis

• Display the towers and numbers in order from 1–10 with 9 missing.
• “¿Qué número falta? ¿Cómo lo saben? // “What number is missing? How do you know?”
• “¿Usaron los números o las torres como ayuda para descubrir lo que faltaba?” // “Did you use the numbers or the towers to help you figure out what was missing?”
• Invite previously selected groups to share how they used 1 more or 1 less with towers or numbers to figure out what number was missing.

## Activity 2: Uno menos, uno más (15 minutes)

### Narrative

The purpose of this activity is for students to identify the number that is 1 less or 1 more than a given number. Students build cube towers and write numbers to match. Students can then find 1 less or 1 more, using the number or the cube towers for support.

MLR8 Discussion Supports. Invite students to chorally repeat phrases that include “uno más que” // “one more than,” and “uno menos que” // “one less than" to increase opportunities for verbal output.
Engagement: Develop Effort and Persistence. Students might benefit from counting the first tower that was built to determine how many cubes they need to create a tower that is 1 fewer or 1 more. Invite students to count in sequence the number of cubes and remind them to stop at the number that is 1 less or 1 more.
Supports accessibility for: Memory, Attention, Organization

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• “Van a trabajar con su pareja para encontrar 1 menos y 1 más” // “You will work with your partner to find 1 less and 1 more.”
• “Hagamos uno juntos” // “Let’s do one together.”
• “Primero, una persona arma un torre con los cubos y escribe un número para mostrar cuántos cubos hay en la torre” // “First, one person builds a tower with the cubes and writes down a number to show how many cubes are in the tower.”
• Make a tower with 7 cubes and write the number 7.
• “Después, su pareja hace una torre nueva que tenga o 1 cubo más o 1 cubo menos que esa torre” // “Then, their partner makes a new tower with either 1 fewer or 1 more cube than this tower.”
• “¿Cuántos cubos puede haber en la nueva torre que armemos?” // “How many cubes can be in the new tower we make?” (6 or 8)
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.
• “Podemos hacer una torre con 6 cubos porque 6 es 1 menos que 7. Entonces, escribimos el número 6” // “We can make a tower with 6 cubes because 6 is 1 less than 7. Then we write the number 6.”
• Build a tower with 6 cubes and write the number 6.
• “Ahora describamos nuestras torres usando las palabras ‘uno menos’ o ‘uno más’” // “Now, describe our towers using the words ‘one fewer’ or ‘one more.’” (The tower with 6 has 1 fewer cube than the tower with 7. The tower with 7 has 1 more cube than the tower with 6.)
• 30 seconds: quiet think time
• 30 seconds: partner discussion
• Share responses.
• Give each group 10 connecting cubes.
• “Ahora es su turno de jugar en parejas” // “Now it is your turn to play with your partner.”

### Activity

• 10 minutes: partner work time

### Student Facing

mi torre

la torre de mi pareja

mi torre

la torre de mi pareja

mi torre

la torre de mi pareja

mi torre

la torre de mi pareja

### Activity Synthesis

• Invite a student to share a tower and number they recorded.
• Escoge una torre de cubos. ¿Qué números puedes usar para mostrar 1 más y 1 menos?” // “What cube towers and numbers can we record to show 1 more and 1 less?”

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

### Narrative

The purpose of this activity is for students to choose activities that offer practice with number and counting concepts

• Math Stories
• Math Libs
• Number Race

### Required Materials

Materials to Gather

### Required Preparation

• Gather materials from:
• Math Stories, Stage 1
• Math Libs, Stage 1
• Number Race, Stage 1

### Launch

• “Hoy vamos a escoger centros de los que ya conocemos” // “Today we 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 qué quieren hacer ahora” // “Choose what you would like to do next.”
• 8 minutes: center work time

### Student Facing

Escoge un centro.

Historias matemáticas

Mi mate-libreta

Carrera con números

### Activity Synthesis

• “¿Qué les gustó de las actividades en las que trabajaron hoy?” // “What did you like about the activities you worked on today?”

## Lesson Synthesis

### Lesson Synthesis

“Hoy encontramos 1 menos y 1 más que un número dado. Díganle a su pareja cómo pueden averiguar cuál número es 1 menos que 9” // “Today we found 1 less and 1 more than a given number. Tell your partner how you can figure out what number is 1 less than 9.” (I can count and figure out what number I say right before 9. I can use cube towers and look for the tower before 9.)

“Practiquemos cómo contar hasta 20” // “Let’s practice counting to 20.”

Demonstrate counting to 20. Count to 20 as a class 1–2 times.