# Lesson 3

Suma a tu manera

## Warm-up: Conversación numérica: Centenas, decenas y unidades (10 minutes)

### Narrative

The purpose of this Number Talk is to elicit strategies and understandings students have for adding three-digit numbers. These understandings help students develop fluency and will be helpful later in this lesson when students are to use strategies based on place value and properties of operations to add within 1,000.

### 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

• Keep expressions and work displayed.
• Repeat with each expression.

### Student Facing

Encuentra mentalmente el valor de cada expresión.

• $$200 + 40 + 7$$
• $$50 + 300 + 2$$
• $$40 + 600 + 12$$
• $$500 + 17 + 130$$

### Activity Synthesis

• “¿Cómo usaron el valor posicional para encontrar el valor de cada suma?” // “How did you use place value to find the value of each sum?” (I added hundreds with hundreds and tens with tens.)
• “¿Alguien puede expresar el razonamiento de _______ de otra forma?” // “Who can restate _______ 's reasoning in a different way?”
• “¿Alguien usó la misma estrategia, pero la explicaría de otra forma?” // “Did anyone have the same strategy but would explain it differently?”
• “¿Alguien pensó en el problema de otra forma?” // “Did anyone approach the problem in a different way?”
• “¿Alguien quiere agregar algo a la estrategia de ____?” // “Does anyone want to add on to____’s strategy?”

## Activity 1: Estrategias para sumar (25 minutes)

### Narrative

The purpose of this activity is for students to add within 1,000 using any strategy that makes sense to them. The expressions in this activity give students a chance to use different strategies, such as adding hundreds to hundreds, tens to tens, and ones to ones, reasoning with numbers close to a hundred, or using a variety of representations. Students who use base-ten blocks or draw number line diagrams choose appropriate tools strategically (MP5).

Engagement: Provide Access by Recruiting Interest. Leverage choice around perceived challenge. Invite students to select 3 of the 4 expressions to complete. Encourage the completion of the last two expressions, as they will be the focus of the synthesis.
Supports accessibility for: Organization, Attention, Social-emotional skills

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• “Por un minuto, piensen cómo podrían encontrar el valor de cada suma” // “Take a minute to think about how you could find the value of each sum.”
• 1 minute: quiet think time
• Share responses.

### Activity

• “Con su pareja, sumen estos números de cualquier forma que tenga sentido para ustedes. Expliquen o muestren su razonamiento” // “Work with your partner to add these numbers in any way that makes sense to you. Explain or show your reasoning.”
• 5-7 minutes: partner work time
• Monitor for an expression for which students use a variety of representations, such as:
• Using base-ten blocks
• Drawing a number line
• Writing their reasoning in words
• Writing equations
• Identify students using different representations to share during synthesis.

### Student Facing

Encuentra el valor de cada suma de cualquier forma que tenga sentido para ti. Explica o muestra tu razonamiento.

1. $$325 + 102$$
2. $$301 + 52$$
3. $$276 + 118$$
4. $$298 + 305$$

### Activity Synthesis

• Select previously identified students to display their work side-by-side for all to see.
• “¿Cuáles representaciones muestran la misma idea o nos ayudan a encontrar la suma de la misma forma?” // “Which representations show the same idea or help us find the sum the same way?” (The base-ten blocks and equations show adding hundreds to hundreds, tens to tens, and ones to ones. The number line and the words both added on the second number to the first number in parts.)

## Activity 2: Dos maneras de sumar (10 minutes)

### Narrative

The purpose of this activity is for students to see that they can start adding from the largest place-value unit or from the smallest and still get the same sum. This understanding prepares students to use the standard algorithm for addition, which calls for starting with the ones.

MLR6 Three Reads: Keep books or devices closed. Display only the problem stem, without revealing the question. “Vamos a leer este problema 3 veces” // “We are going to read this problem 3 times.” After the 1st Read: “Cuéntenle a su pareja de qué se trata esta situación” // “Tell your partner what this situation is about.” After the 2nd Read: “Hagan una lista de las cantidades. ¿Qué se puede contar o medir?” // “List the quantities. What can be counted or measured?” Reveal the question(s). After the 3rd Read: “¿Qué estrategias podemos usar para resolver este problema?” // “What strategies can we use to solve this problem?”

### Launch

• Groups of 2
• “Por un minuto, miren el trabajo de Andre y el trabajo de Clare. Piensen en qué se parecen y en qué son diferentes” // “Take a minute to look at Clare and Andre’s work. Think about how their work is alike and how it's different.”
• 1 minute: quiet think time

### Activity

• “Hablen en parejas sobre en qué se parecen y en qué se diferencian el trabajo de Clare y el trabajo de Andre” // “Talk with your partner about what’s different about Clare and Andre’s work and what’s the same.”
• 3-5 minutes: partner discussion

### Student Facing

Andre encontró el valor de $$276 + 118$$. Este es su trabajo.

$$200 + 100 = 300$$
$$70 + 10 = 80$$
$$6 + 8 = 14$$
$$300 + 80 + 14 = 394$$

Clare encontró el valor de $$276 + 118$$. Este es su trabajo.

$$6 + 8 = 14$$
$$70 + 10 = 80$$
$$200 + 100 = 300$$
$$14 + 80 + 300 = 394$$

Con tu pareja, discute:

• ¿En qué son diferentes el trabajo de Andre y el trabajo de Clare?
• ¿En qué se parecen?

### Activity Synthesis

• Invite students to share their responses.
• “Si fueran a describir los pasos que Andre siguió para sumar y los pasos que Clare siguió para sumar, ¿cuáles serían estos?” // “If you were to describe the steps that Andre took to add and the steps that Clare took to add, what would they be?” (Andre added the hundreds, added the tens, added the ones, then added up all the parts to find the sum. Clare added the ones, added the tens, added the hundreds, then added up the parts to find the sum.)
• “¿Por qué si Andre empezó con las centenas y Clare empezó con las unidades, los dos encontraron la misma suma?” // “How is it that Andre started with the hundreds and Clare started with the ones, but they both found the same sum?” (It doesn’t matter the order that we add the numbers. If they’re the same numbers we’ll get the same sum.)

## Lesson Synthesis

### Lesson Synthesis

“Hoy sumamos números usando diferentes estrategias y representaciones. ¿Cuál es la representación que prefieres usar cuando sumas números?” // “Today we added numbers using many different strategies and representations. What is your favorite representation to use when you add numbers?” (Sample responses: I like to use base-ten blocks so I can see the numbers I am adding. I like to write equations because it shows me how I am adding the numbers.)

“¿La manera en la que suman números o la representación que usan cambia de acuerdo a los números del problema?” // “Does the way you add numbers or the representation you use change based on the numbers in the problem?” (Sample responses: Yes, I use mental math when I see that one of the numbers is close to a hundred. No, I always add hundreds to hundreds, tens to tens, and ones to ones. I always like to draw a number line.)

“En las próximas lecciones, tengan presentes todas estas estrategias cuando aprendamos nuevas formas de mostrar nuestro razonamiento al sumar” // “Keep all these strategies in mind as we learn new ways to show our reasoning when adding in the upcoming lessons.”