Lesson 6
Usemos una decena para sumar hasta 1,000
Warm-up: Conversación numérica: Números que forman 10 (10 minutes)
Narrative
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 students’ thinking on an open number line and with equations.
- Keep expressions and work displayed.
- Repeat with each expression.
Student Facing
Encuentra mentalmente el valor de cada expresión.
- \(28 + 2\)
- \(28 + 12\)
- \(67 + 3\)
- \(67 + 23\)
Student Response
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Activity Synthesis
- “¿En qué se parecen todas las expresiones?” // “What’s the same about all of the expressions?” (I made a ten to find the value for each of them.)
- “¿Por qué \(28 + 2\) y \(67 + 3\) ayudan a encontrar el valor de las otras expresiones?” // “Why are \(28 + 2\) and \(67 + 3\) helpful in finding the value of the other expressions?” (We made ten and then added 1 more ten.)
- “En la siguiente actividad, vamos a seguir pensando en cómo nos puede ayudar sabernos las sumas de 10” // “In the next activity, we are going to keep thinking about how knowing sums of 10 can help us.”
Activity 1: Sumemos números de dos dígitos y de tres dígitos (15 minutes)
Narrative
Required Materials
Materials to Gather
Launch
- Groups of 3
- Give students access to base-ten blocks.
Activity
- “En su grupo, cada uno de ustedes va a encontrar el valor de un conjunto de expresiones” // “In your group, each of you will find the value of one set of expressions.”
- Make sure students know which set they will work with.
- “Mientras trabajan, piensen sobre los patrones que observan” // “As you work, think about patterns you notice.”
- “Si les ayuda, pueden usar bloques en base diez” // “If it helps, you may use base-ten blocks.”
- 6 minutes: independent work time
- “Comparen con los miembros de su grupo y discutan los patrones que observaron” // “Compare with your group members and discuss any patterns you noticed.”
- 4 minutes: partner discussion
Student Facing
-
Encuentra el valor de cada suma.
Conjunto 1
Conjunto 2
Conjunto 3
\(245 + 15\)
\(134 + 26\)
\(351 + 19\)
\(247 + 23\)
\(133 + 37\)
\(356 + 24\)
\(249 + 31\)
\(138 + 42\)
\(355 + 35\)
- ¿Qué patrones observaste?
Student Response
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Advancing Student Thinking
If students find a sum other than the sum of the two numbers, consider asking:
- “¿Puedes explicar cómo encontraste la suma?” // “Can you explain how you found the sum?”
- “¿Cómo puedes usar una recta numérica o bloques en base diez para mostrar cómo pensaste?” // “How could you use a number line or base-ten blocks to show your thinking?”
Activity Synthesis
- “¿Qué patrones observaron en cada conjunto?” // “What patterns did you notice in each set?” (Each time we could make a ten with the ones. The number of hundreds didn't change. The sums went up by 10.)
- Share and record responses.
- “Saben que \(6 + 4 = 10\). ¿Cómo les ayuda eso a pensar en \(536 + 34\)?” // “How does knowing \(6 + 4 = 10\) help you think about \(536 + 34\)?” (I can add \(530 + 30 = 560\). Then add 10 because I know \(6 + 4 = 10\).)
Activity 2: Clasificación de tarjetas: Decena perfecta (20 minutes)
Narrative
The purpose of this activity is for students use what they know about combinations of 10 to identify when a ten will be composed when adding a three-digit number and a two-digit number by place. Students are given a set of cards with three-digit numbers and two-digit numbers and work with their group to decide which numbers will make a ten with no extra ones when they are added together (a “perfect ten”). After finding all the matches, each group member chooses a pair and finds the value of the sum. In the synthesis, students discuss how they could tell a pair of numbers would make a ten by looking at the digits in the ones place. In upcoming lessons, students will use this understanding to anticipate when they may need to compose units when they add 2 three-digit numbers.
When they match numbers whose ones combine to make ten students look for and identify structure which can be helpful when finding sums (MP7).
Advances: Conversing, Reading
Supports accessibility for: Conceptual Processing
Required Materials
Required Preparation
- Create a set of cards from the blackline master for each group of 3.
Launch
- Groups of 3–4
- Give each group a set of cards and access to base-ten blocks.
Activity
- “Este grupo de tarjetas incluye números de tres dígitos y números de dos dígitos. Emparejen cada número de tres dígitos con un número de dos dígitos, de tal manera que cuando los sumen formen una decena sin unidades adicionales. Cuando esto ocurre, vamos a decir que dos números forman una ‘decena perfecta’” // “This set of cards includes three-digit numbers and two-digit numbers. Match each three-digit number to a two-digit number, so that when you add them together they will make a ten with no extra ones. When this happens, we are going to say the two numbers make a ‘perfect ten.’”
- “Con su pareja, justifiquen sus elecciones” // “Work with your partner to justify your choices.”
- As needed, provide an example of two numbers that make a “perfect ten” from the previous activities.
- “Después de encontrar todas las parejas, cada miembro del equipo debe escoger una pareja de números diferente y encontrar su suma” // “After finding all the matches, each group member should choose a different pair of numbers and find their sum.”
- “Si queda tiempo, intercambien las tarjetas o escojan otra pareja de números” // “If there is time, switch cards or pick another pair.”
- 15 minutes: small-group work time
- Monitor for groups who focus on finding combinations of 10 in the ones place and explain their reasoning.
- Monitor for students to share how they add their pair of numbers to share in the lesson synthesis.
Student Facing
- Empareja cada número de tres dígitos con un número de dos dígitos. Cuando sumes tus números, ellos deben formar una decena sin unidades adicionales.
-
Escoge 1 pareja de números y encuentra el valor de su suma. Muestra cómo pensaste.
Student Response
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Activity Synthesis
- Invite groups to share the matches they made and how they know those cards go together.
- Attend to the language that students use to describe their matches, giving them opportunities to describe how they knew adding the numbers would result in composing a ten with no extra ones more precisely.
Lesson Synthesis
Lesson Synthesis
“Hoy aprendieron que cuando le suman un número de dos dígitos a un número de tres dígitos, saberse las sumas de 10 puede ayudarlos a saber si deberán componer una decena” // “Today you learned that when you add a two-digit number to a three-digit number, knowing sums of 10 can help you tell if you will need to compose a ten.”
Invite previously identified students to share how they found the value of their sums.
Share and record responses.
Cool-down: Encuentra la suma (5 minutes)
Cool-Down
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