The purpose of this Number Talk is to elicit the ways students look for to use the structure of two-digit numbers to subtract (MP7). These understandings help students develop fluency and will be helpful later in this lesson when students will need to be able to find the difference between the estimate and actual measurement of an object.
Launch
Display one expression.
“Hagan una señal cuando tengan una respuesta y puedan explicar cómo la obtuvieron” // “Give me a signal when you have an answer and can explain how you got it.”
1 minute: quiet think time
Activity
Record answers and strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Task Statement
Encuentra mentalmente el valor de cada expresión.
Student Response
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Advancing Student Thinking
Activity Synthesis
“¿Cómo podrían usar como ayuda para encontrar ?” // “How could you use to help you with ?”
Activity 1
15 mins
Retomemos “Acertijos numéricos: Hasta 100 componiendo”
Standards Alignment
Building On
Addressing
2.NBT.B.5
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
The purpose of this activity is for students to revisit Stage 4 of the Number Puzzles center which was first introduced in grade 1. Students work together to use digit cards to make addition and subtraction equations within 100 with composing and decomposing true. Each digit (0–9) can only be used once in a puzzle. Puzzles with less than ten spaces will have leftover cards.
Launch
Groups of 2
Give each group a set of digits (0–9) and a set of gameboards.
“Ahora vamos a aprender una nueva forma de jugar el centro ‘Acertijos numéricos’” // “Now we are going to learn a new way to play the Number Puzzles center.”
“En esta etapa, ustedes usan sus tarjetas de dígitos para hacer que cada ecuación sea verdadera. Es posible que tengan que pensar en componer o en descomponer una decena. Recuerden que en cada acertijo solo pueden usar un dígito una vez y que en algunos acertijos van a quedar tarjetas sin usar” // “In this stage, you use your digit cards to make each equation true. You may need to think about composing or decomposing a ten. Remember that you can only use a digit once in a puzzle and some puzzles will have leftover cards.”
Activity
10 minutes: partner work time
Student Task Statement
None
Student Response
None
Advancing Student Thinking
Activity Synthesis
Display a gameboard.
“¿Qué ecuación pueden completar primero?” // “Which equation can you fill in first?”
The purpose of this activity is for students to choose from activities that focus on addition and subtraction within 100 or story problems. Students choose from previously introduced stages of these centers:
Number Puzzles
Math Stories
Launch
“Ahora van a escoger centros de los que ya conocemos. Una de las opciones es seguir con ‘Acertijos numéricos’” // “Now you will choose from centers we have already learned. One of the choices is to continue with Number Puzzles.”
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 les gustaría hacer ahora” // “Choose what you would like to do next.”
8 minutes: center work time
Student Task Statement
Escoge un centro.
Acertijos numéricos
Historias matemáticas
Student Response
None
Advancing Student Thinking
Activity Synthesis
“¿Qué les gustó de la actividad en la que trabajaron hoy?” // “What did you like about the activity you worked on today?”
Lesson Synthesis
“Hoy usamos tarjetas de dígitos para completar ecuaciones que tenían números desconocidos. Cuéntenle a su compañero algo que les haya ayudado a descifrar cómo completar la ecuación” // “Today, we used digit cards to complete equations with missing numbers. Tell your partner something that helped you figure out how to complete the equation.”
Standards Alignment
Building On
Addressing
2.NBT.B.5
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.