Lesson 3

Sumemos o restemos para resolver problemas-historia

Warm-up: Cuántos ves: Diagrama en base diez (10 minutes)

Narrative

The purpose of this How Many Do You See is to build on what students know about place value to make sense of a visual representation of two-digit numbers. When students describe how many they see by grouping tens with tens and ones with ones or composing a ten, they show how they look for and make use of base-ten structure (MP7). This will be helpful when students use base-ten representations to compose and decompose a ten in future lessons.

Launch

• Groups of 2
• “¿Cuántos ven? ¿Cómo lo saben?, ¿qué ven?” // “How many do you see? How do you see them?”
• Flash the image.
• 30 seconds: quiet think time

Activity

• Display the image.
• “Discutan con su pareja cómo pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• Repeat for each image.

Student Facing

¿Cuántos ves? ¿Cómo lo sabes?, ¿qué ves?

Activity Synthesis

• “¿Como supieron cuántos había en la tercera imagen?” // “How did you know how many were in the third image?”
• “¿Como podemos representar este número de otra manera?” // “How could we represent this number another way?” (Instead of 10 ones, we could use a ten.)

Activity 1: Diversión en el zoológico (20 minutes)

Narrative

The purpose of this activity is for students to interpret and solve a story problem by adding or subtracting within 100. Students solve an Add To, Start Unknown problem, one of the more difficult problem types from grade 1. Students begin the activity by looking at the problem displayed, rather than in their books. At the end of the launch, students open their books and work on the problem.

Monitor for students who use methods that show adding or subtracting by place to share in the synthesis. Students who choose to use connecting cubes or base-ten blocks or who draw a diagram to represent the situation are using tools strategically (MP5). During the synthesis, invite all students to explain why these methods work using their understanding of place value.

This activity uses MLR6 Three Reads. Advances: reading, listening, representing. Some students may benefit from continued use of MLR6 to support reading comprehension in Activity 2.

Required Materials

Materials to Gather

Launch

• Groups of 2
• “¿Alguna ves han ido a una excursión? ¿A dónde fueron?” // “Have you ever been on a field trip? Where did you go?”
• “En su excursión, ¿las personas estuvieron siempre juntas o se separaron en grupos más pequeños?” // “Did everyone on your field trip stay together the whole time or did you split into smaller groups?”

• Display only the story problem, without revealing the question.
• “Vamos a leer este problema 3 veces” // “We are going to read this problem 3 times.”
• 1st Read: “Algunos estudiantes estaban en un bus que iba al zoológico. Después, 34 estudiantes más se subieron. Ahora hay 55 estudiantes en el bus” //  “Some students were on the bus to go to the zoo. Then 34 more students got on. Now there are 55 students on the bus.”
• “¿De qué se trata esta historia?” // “What is this story about?”
• 1 minute: partner discussion.
• Listen for and clarify any questions about the context.
• 2nd Read: “Algunos estudiantes estaban en un bus que iba al zoológico. Después, 34 estudiantes más se subieron. Ahora hay 55 estudiantes en el bus” // “Some students were on the bus to go to the zoo. Then 34 more students got on. Now there are 55 students on the bus.”
• “¿Cuáles son todas las cosas de esta historia que podemos contar?” // “What are all the things we can count in this story?” (number of students who started the story on the bus, number of students who got on next, the total number of students on the bus, the number of buses)
• 30 seconds: quiet think time
• 2 minutes: partner discussion
• Share and record all quantities.
• Reveal the question.
• “¿De qué formas diferentes podemos resolver este problema?” // “What are different ways we can solve this problem?” (We could subtract the number of students who got on the bus second from the total. We could add to the number of students who got on the bus until we get to the total.)
• 30 seconds: quiet think time
• 1–2 minutes: partner discussion

Activity

• 5 minutes: independent work time
• Monitor for students who:
• use base-ten blocks or base-ten diagrams to show adding tens to tens or ones to ones
• use base-ten blocks or base-ten diagrams to show subtracting from tens or ones from ones

Student Facing

Algunos estudiantes estaban en un bus que iba al zoológico. Después, 34 estudiantes más se subieron. Ahora hay 55 estudiantes en el bus. ¿Cuántos estudiantes había en el bus al comienzo?

Activity Synthesis

• Invite previously identified students to share.
• Record student methods using equations.
• “¿En qué se parecen estos métodos?” // “How are these methods the same?” (They both show tens and ones. They both thought of keeping the tens with the tens and ones with the ones.)

Activity 2: Más diversión en el zoológico (15 minutes)

Narrative

The purpose of this activity is to solve different story problems by adding or subtracting within 100 without composing or decomposing a ten. Each problem elicits the relationship between addition and subtraction and can be solved with either operation. Students are encouraged to describe methods based on place value and should have access to base-ten blocks. In the synthesis, students compare representations and make connections between concrete representations and drawings.

Invite students to use the Three Reads routine to support reading comprehension. Some students may also benefit from reading the story problems with their partner before working independently.

Representation: Develop Language and Symbols. Synthesis: Invite students to explain their thinking orally, using the connecting cubes or base-ten blocks, while students work independently. Check in frequently to make sure the students are making connections between the story and the cubes or blocks.
Supports accessibility for: Language, Visual-Spatial Processing

Required Materials

Materials to Gather

• Groups of 2

Activity

• 6 minutes: independent work time
• 4 minutes: partner discussion
• Monitor for students who use base-ten blocks and students who use base-ten diagrams to represent methods based on adding or subtracting by place.

Student Facing

Resuelve cada problema-historia. Muestra cómo pensaste.

1. Había 65 estudiantes en la casa de los monos. 23 se fueron a ver los hipopótamos. ¿Cuántos estudiantes quedaron en la casa de los monos?
2. 58 estudiantes fueron a ver los osos. 27 estudiantes fueron a ver los leones. ¿Cuántos estudiantes más fueron a ver los osos que los leones?
3. Algunos pájaros estaban en jaulas afuera de la casa de pájaros. 34 pájaros estaban dentro de la casa de pájaros. En total había 88 pájaros. ¿Cuántos estaban en las jaulas afuera?

Student Response

If students do not show evidence of grouping tens and ones, consider asking:

• “¿Qué hiciste para resolver el problema-historia?” // “What did you do to answer the story problem?”
• “¿Cómo usaste lo que sabes sobre decenas y unidades para sumar o restar?” // “How could you use what you know about tens and ones to add or subtract?”

Activity Synthesis

• Invite previously identified students to share. Consider selecting a student who used base-ten blocks first, followed by a student who used a base-ten drawing.
• If no students use a base-ten drawing, draw one to record the way a student uses their blocks to represent and solve the problem.
• “¿En qué se parecen estas representaciones?” // “How are these representations the same?” (Both started by representing 88 birds. _____ moved away 3 tens and 4 ones and _____ crossed out 3 tens and 4 ones.)
• 1 minute: quiet think time
• Share responses.

Lesson Synthesis

Lesson Synthesis

Display a base-ten diagram from Activity 2 that was shared in the activity synthesis.

“Pensemos qué ecuaciones se nos ocurren que correspondan a la manera en que _____ usó su diagrama” // “Let’s come up with equations we could write to match how _____ used their diagram.” ($$80 - 30 = 50$$, $$8 - 4 =4$$, $$50 + 4 = 54$$)

Cool-down: Hora de irse (5 minutes)

Cool-Down

$$50 - 30 = 20$$
$$5 - 4 = 1$$
$$20 + 1 = 21$$