# Lesson 10

Escribamos acertijos numéricos

## Warm-up: Verdadero o falso: Sumemos hasta 100 (10 minutes)

### Narrative

The purpose of this True or False is to elicit strategies and understandings students have for adding within 100.

### 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 strategies.
• Repeat with each equation.

### Student Facing

Prepárate para explicar tu razonamiento.

• $$60 = 25 + 45$$

• $$70 = 24 + 46$$

• $$80 = 32 + 37$$

### Activity Synthesis

• “¿Cómo pueden explicar su respuesta sin encontrar el valor de las sumas que están en el lado derecho?” // “How can you explain your answer without finding the value of the sums on the right side?”

## Activity 1: Escribamos acertijos numéricos (15 minutes)

### Narrative

The purpose of this activity is for students to write number riddles. Students choose a secret number between 1 and 120, and write four clues that will help their classmates identify the number. As students work, the teacher should review students’ riddles and monitor for groups that may need help writing clues.

Representation: Develop Language and Symbols. Maintain a visible display to record terms and phrases that will be useful in writing Number Riddles such as: number of tens, number of ones, more than, less than.
Supports accessibility for: Memory, Language

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give each group four index cards, a bag or envelope, and access to connecting cubes in towers of 10 and singles.
• “¿Qué tipos de pistas vimos cuando resolvimos acertijos numéricos?” // “When we solved number riddles, what types of clues did we see?” (number of tens, number of ones, more than, less than, addition)
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Record responses.

### Activity

• “Ahora van a escribir un acertijo con su compañero. Van a escribir cuatro pistas. Una pista debe ser una expresión de suma, y esa será la última pista. Escriban cada pista en una tarjeta y asegúrense de que su número se ajuste a todas las pistas. Doblen por la mitad la tarjeta que tiene la expresión de suma” // “Now you will write a number riddle with your partner. You will write four clues. One clue should be an addition expression that will be the last clue. Write each clue on an index card and make sure that your number fits all the clues. Fold the card with the addition expression in half.”
• 10 minutes: partner work time
• “¿Cuál es su número secreto?” // “What is your secret number?”
• “¿Su número secreto es mayor que cuál número (o números)? ¿Es menor que cuál número (o números)?” // “What number(s) is your secret number greater than? Less than?”
• “¿Qué saben sobre las decenas y las unidades de su número secreto?” // “What do you know about the tens and ones in your secret number?”
• “¿Qué números pueden sumar (restar) para obtener este número?” // “What numbers can you add (subtract) to get this number?”

### Student Facing

Nuestro número secreto: ____________
Nuestras 4 pistas:

• Escriban cada pista en una tarjeta.
• Asegúrense de que la última pista sea una expresión de suma.
• Doblen esa pista por la mitad.

### Student Response

If students write fewer than three clues, consider asking:

• “¿Qué sabes sobre tu número secreto?” // “What do you know about your secret number?”
• “¿Cómo puedes escribir una pista usando las palabras ‘mayor que’, ‘menor que’ o ‘__ decenas o unidades’?” // “How can you write a clue using ‘greater than’ or ‘less than’ or __ tens or ones?”

### Activity Synthesis

• “Pongan sus pistas en un sobre y escriban sus nombres en el sobre” // “Put your clues in an envelope and write your names on the envelope.”

## Activity 2: Resolvamos nuestros acertijos numéricos (20 minutes)

### Narrative

The purpose of this activity is for students to apply place value reasoning to solve number riddles written by their classmates. When students solve the number riddles they use their understanding of the number sequence and place value (MP7).

MLR8 Discussion Supports. Students should take turns reading clues and explaining their reasoning to their partner. Display the following sentence frames for all to see: “Observé _____, entonces yo . . .” // “I noticed _____ , so I . . .” Encourage students to challenge each other when they disagree.

### Required Materials

Materials to Gather

### Required Preparation

• Each group of 2 needs to begin with a riddle envelope from the previous activity.

### Launch

• Groups of 2
• Give each group a riddle envelope and access to connecting cubes in towers of 10 and singles.

### Activity

• “Ahora van a resolver los acertijos de sus compañeros. Usen las páginas de su libro de trabajo para anotar sus ideas mientras resuelven los acertijos. Cuando terminen de resolver un acertijo, pónganlo en el sobre y busquen otro grupo que esté listo para intercambiar el acertijo con ustedes” // “Now you are going to solve your classmates’ riddles. Use your workbook page as a place to record your ideas as you solve. When you finish solving a riddle, put it back in the envelope and look for another group who is ready to trade riddles with you.”
• 15 minutes: partner work time

### Student Facing

Anoten sus ideas mientras resuelven cada acertijo numérico.

### Activity Synthesis

• “¿Hubo acertijos numéricos que fueran retadores? ¿Por qué fueron más retadores que los otros acertijos?” // “Were there any number riddles that were challenging to solve? Why were they more challenging than the other riddles?”

## Lesson Synthesis

### Lesson Synthesis

“Compartan con su compañero el trabajo que hicieron en el cierre” // “Share your work from the cool-down with your partner.”

Invite students to share with the whole class.