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Activity 1

20 mins

Observemos la diferencia

Standards Alignment

Building On

Addressing

Building Toward

Instructional Routines

None

Materials

None

Activity Narrative

The purpose of this activity is for students to compare three-digit numbers and find the value of their difference. Students used the number line to compare three-digit numbers in an earlier unit. They build on this understanding as they find the difference between 2 three-digit numbers that are within 10 of one another on the number line. Students notice that when the numbers in a subtraction expression are close together, they can count on or count back to find the value of the difference (MP7, MP8).

Engagement: Provide Access by Recruiting Interest. Optimize meaning and value. Invite students to represent the jumps/movement on the number line, using an animal such as a frog, a rabbit, or a grasshopper. Focus on the minimal jumping the animal does when the numbers are close on the number line.
Supports accessibility for: Conceptual Processing, Attention

Launch

Groups of 2

Activity

“A Tyler y a Elena les pidieron que encontraran el valor de . Este es su trabajo” // “Tyler and Elena were asked to find . This is their work.”
“¿Qué observan? ¿Qué se preguntan?” // “What do you notice? What do you wonder?” (The numbers are close on the number line. Tyler has drawn all the tens and ones for 81 and subtracted almost all the tens and ones. Why did Elena put a point on 79 and count up instead of subtracting 79?)
“En una lección anterior aprendieron que pueden restar quitando una cantidad. También aprendieron que pueden contar hacia adelante desde un número hasta otro o contar hacia atrás desde un número hasta otro para encontrar la diferencia entre los 2 números” // “You have learned in an earlier lesson that you can subtract by taking an amount away. You also learned you can count on or count back from one number to the other to find the difference between the 2 numbers.”
“Esto también funciona con números de tres dígitos” // “This works with three-digit numbers, too.”
“Resuelvan los siguientes problemas solos y después comparen con un compañero cómo pensaron” // “Do the next few problems on your own, and then compare your thinking with a partner.”
8 minutes: independent work time
4 minutes: partner discussion
Monitor for students who count on or count back.

Activity Synthesis

Invite previously identified students to share how they found the value of .
As time permits, invite students to share their comparisons and how they found the value of each difference.
“¿Qué observaron sobre los números cuándo los ubicaron en la recta numérica?” // “What did you notice about the numbers when you located them on the number line?” (They were close together. It was easy to see a way to just count from one number to the other.)

Activity 2

15 mins

¿Cuál es la gran diferencia?

Standards Alignment

Building On

Addressing

Building Toward

Instructional Routines

None

Materials

None

Activity Narrative

The purpose of this activity is for students to use what they know about counting within 1,000 to make sense of number lines that show counting on or counting back by 10 or by 100. This work helps build fluency with counting within 1,000, and connects to an upcoming lesson where students add and subtract multiples of 10 or 100, using equations.

MLR8 Discussion Supports. Invite students to begin partner interactions by repeating the question, “¿Qué patrón observan?” // “What pattern do you notice?” This gives both students an opportunity to produce language.
Advances: Conversing

Launch

Groups of 2
Display the number line with jumps of 100.
“En esta recta numérica hay 5 marcas, pero solo 3 tienen el número escrito debajo. ¿Cuáles son los números desconocidos y cómo lo saben?” // “On this number line there are 5 tick marks, but only 3 are labeled. What are the missing numbers, and how do you know?” (534 and 634, because the jumps are the same length and they must be jumps of 100. The hundreds place is increasing by 1, but the other places are not changing.)
30 seconds: quiet think time
30 seconds: partner discussion
Share and record responses.
“Ustedes reconocieron que la longitud entre cada marca debe representar 100. Las marcas y flechas muestran que se está contando hacia adelante de 100 en 100 en la recta numérica” // “You recognized that the length between each tick mark must represent 100. The tick marks and arrows show counting on by 100 on the number line.”

Activity

“En cada uno de los problemas, usen lo que saben sobre contar, representar números en la recta numérica y el valor posicional para encontrar los números desconocidos” // “For each of the problems, use what you know about counting, representing numbers on the number line, and place value to find the missing numbers.”
10 minutes: partner work time
Monitor for a student to share their reasoning for _____, _____, 332, 342, 352

Student Task Statement

Escribe los números desconocidos.

¿Esta recta numérica muestra que se está contando hacia adelante de 10 en 10 o de 100 en 100?
Escribe los números desconocidos.

¿Esta recta numérica muestra que se está contando hacia adelante de 10 en 10 o de 100 en 100?
Escribe los números desconocidos.

¿Esta recta numérica muestra que se está contando hacia adelante de 10 en 10 o de 100 en 100?
Escribe los números desconocidos para mostrar que se está contando de 10 en 10.

739, 749, __________, 769, __________
Explica cómo sabes que tus números muestran que se está contando hacia adelante de 10 en 10, y no de 100 en 100.

Student Response

to access Student Response.

Advancing Student Thinking

If students find the unknown numbers by counting by 1 instead of by using patterns of increasing by 10 or by 100, consider asking:

“¿Qué dígito está cambiando? ¿Está aumentando o disminuyendo?” // “What digit is changing? Is it going up or down?”
“¿Cómo puede ayudarte eso a descifrar el conteo que se está haciendo?” // “How can that help you figure out the count?”

Are You Ready for More?

Activity Synthesis

Invite a student to share their reasoning for _____, _____, 332, 342, 352.
“¿Cómo descifraron cuál era el primer número?” // “How did you figure out the starting number?” (I saw that it was going up by 10, so I knew I had to count back by 10 to find the starting numbers.)
Record responses with an open number line and equations.

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Lesson 1

Comparemos, contemos hacia adelante y contemos hacia atrás

Warm-up

Conversación numérica: Contemos hacia atrás

Instructional Routines

Materials

Activity Narrative

Launch

Activity

Student Task Statement

Student Response

Advancing Student Thinking

Are You Ready for More?

Activity Synthesis

Activity 1

Observemos la diferencia

Standards Alignment

2.NBT.7

Instructional Routines

Materials

Activity Narrative

Launch

Activity

Activity Synthesis

Activity 2

¿Cuál es la gran diferencia?

Standards Alignment

2.NBT.2

2.NBT.8

Instructional Routines

Materials

Activity Narrative

Launch

Activity

Student Task Statement

Student Response

Advancing Student Thinking

Are You Ready for More?

Activity Synthesis

Lesson Synthesis

Have feedback on the curriculum?

Standards Alignment

2.NBT.7

Student Task Statement

Student Response

Advancing Student Thinking

Are You Ready for More?

2.NBT.7