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Activity 1

Standards Alignment

Building On

Addressing

Building Toward

Instructional Routines

None

Materials

To Copy (from Blackline Masters)

Number Line to 100 Recording Sheet

Activity Narrative

The purpose of this activity is for students to solve addition and subtraction problems within 100 with the unknown in all positions. Students write equations with a ? for the unknown and find the number that makes the equations true. The mathematical context of each problem encourages students to use the number line to reason about what is unknown and how they may represent the problem with an equation (MP2).

Representation: Access for Perception. Use a small toy animal or cut-out animal, such as a bird, frog, rabbit, or cricket, to demonstrate the jumping on the number line.
Supports accessibility for: Attention, Organization

Launch

Groups of 2
Give each student a copy of the blackline master.
Display an image of a blank number line or draw a number line.
“Hoy van a resolver acertijos para encontrar un número secreto” // “Today you will be solving riddles to find a mystery number.”
“En cada caso, van a escribir una ecuación que le corresponda al acertijo. Usen el signo ? para representar el número desconocido” // “For each riddle, you will write an equation that represents the riddle, and write a ? for the unknown.”
“Luego, van a representar la ecuación en la recta numérica” // “Then you will represent the equation on the number line.”
“Intentemos un acertijo juntos” // “Let’s try one together.”
Demonstrate on a number line with input from the students.
“Empecé en un número y salté 10 hacia la izquierda. Mi salto terminó en el 42. ¿Dónde había empezado?” // “I started on a number and jumped 10 to the left. My jump ended at 42. Where did I start?”
“¿Qué ecuación puedo escribir en la que use el signo ? para representar el número desconocido?” // “What equation could I write with a ? for the unknown?” ()
“¿Cómo puedo encontrar el valor del número secreto?” // “How could I find the value of the mystery number?” (Do the opposite. Start at 42 and move 10 to the right.)
1 minute: quiet think time
1 minute: partner discussion
Share responses and record on the number line.

Activity

“Ahora tendrán la oportunidad de resolver acertijos para encontrar un número desconocido. Luego, van a usar una recta numérica para representar cómo pensaron. Ustedes y su compañero pueden tomar turnos: mientras uno lee el acertijo, el otro lo sigue a lo largo de la recta numérica” // “Now you will have a chance to solve riddles to find a missing number, and then represent your thinking on a number line. You and your partner can take turns reading the riddle, while the other person follows along on the number line.”
12 minutes: partner work time

Resuelve cada acertijo para encontrar el número secreto.

En cada caso:

Escribe una ecuación que le corresponda al acertijo. Usa el signo ? para representar el número desconocido.
Representa la ecuación en la recta numérica. Escribe el número secreto.

Empecé en el 15 y salté 17 hacia la derecha. ¿En dónde terminé?

Ecuación: _______________________________

Número secreto: _______________________
Empecé en un número y salté 20 hacia la izquierda. Terminé en el 33. ¿Dónde había empezado?

Ecuación: _______________________________

Número secreto: _______________________
Empecé en el 42 y terminé en el 80. ¿Cuánto salté?

Ecuación: _______________________________

Número secreto: _______________________
Empecé en el 76 y salté 27 hacia la izquierda. ¿En dónde terminé?

Ecuación: _______________________________

Número secreto: _______________________
Empecé en un número y salté 19 hacia la derecha. Terminé en el 67. ¿Dónde había empezado?

Ecuación: _______________________________

Número secreto: _______________________
Empecé en el 92 y terminé en el 33. ¿Cuánto salté?

Ecuación: _______________________________

Número secreto: _______________________

Number line with endpoints of 50 and 65. Frog hopping on number line from 51 to 56, 56 to 60, and 60 to 63.

Student Response

to access Student Response.

Advancing Student Thinking

If students write equations that do not match the riddle or their number line representation, consider asking:

“¿Cómo decidiste dónde poner tu punto inicial o tu punto final?” // “How do you decide where to put your starting or ending points?”
“¿Qué parte del acertijo te puede ayudar a escoger la dirección de tus flechas y tus saltos?” // “What part of the riddle could help you choose the direction for your arrows and jumps?”

Activity Synthesis

Invite students to share the answer to each riddle and display their number line.
“¿Cuáles acertijos les parecieron más retadores a ustedes y su compañero? Expliquen” // “Which riddles did you and your partner find to be most challenging? Explain.”

Activity 2

Standards Alignment

Building On

Addressing

Building Toward

Instructional Routines

None

Materials

To Copy (from Blackline Masters)

Number Line to 100 Recording Sheet

Activity Narrative

The purpose of this activity is for students to find the value of an unknown in addition and subtraction equations. Students can choose to find the unknown number using either operation and then represent their thinking on a number line. Listen for the ways students use the number line to make sense of the relationship between the numbers in each equation. Also listen for methods that show students are thinking about ways to use the structure of the number line and their understanding of place value (MP7).

MLR8 Discussion Supports.Synthesis: Provide students with the opportunity to rehearse what they will say with a partner before they share with the whole class.
Advances: Speaking

Launch

Groups of 2
Give each student a copy of the blackline master.

Activity

“Encuentren, de una manera que tenga sentido para ustedes, el número que hace que cada ecuación sea verdadera” // “Find the number that makes each equation true in a way that makes sense to you.”
“Usen una recta numérica para mostrar cómo pensaron” // “Represent your thinking on the number line.”
Monitor for a student who finds the value for by:
- Starting at 57, drawing a jump to 72, and counting each length unit in between.
- Staring at 57, drawing a jump of 3 and a jump of 12 to 72.
- Starting at 72 and jumping back 57 in one jump or multiple jumps.

En cada caso, encuentra el número que hace que la ecuación sea verdadera.

Usa una recta numérica para mostrar cómo pensaste.

Student Response

to access Student Response.

Advancing Student Thinking

Activity Synthesis

Invite previously selected students to share how they found the number that makes true.
Consider asking:
- “¿De qué manera la recta numérica de ______ muestra los números que conocíamos? ¿De qué manera muestra el número desconocido?” // “How does ______'s number line show the numbers that we knew? How does it show the unknown number?”
- “¿En qué se parecen estos métodos? ¿En qué son diferentes?” // “How are these methods the same? How are they different?”
As time permits, continue with other equations.

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Lesson 12

Ecuaciones con números desconocidos

Warm-up

Instructional Routines

Materials

Activity Narrative

Launch

Activity

Student Response

Advancing Student Thinking

Activity Synthesis

Activity 1

Standards Alignment

Building On

Addressing

2.MD.B.6

2.NBT.B.5

2.OA.A.1

Building Toward

Instructional Routines

Materials

To Copy (from Blackline Masters)

Activity Narrative

Launch

Activity

Student Response

Advancing Student Thinking

Activity Synthesis

Activity 2

Standards Alignment

Building On

Addressing

2.MD.B.6

2.NBT.B.5

Building Toward

Instructional Routines

Materials

To Copy (from Blackline Masters)

Activity Narrative

Launch

Activity

Student Response

Advancing Student Thinking

Activity Synthesis

Lesson Synthesis

Standards Alignment

Building On

Addressing

2.NBT.B.5

Building Toward