# Lesson 1

## Warm-up: Cuántos ves: Tableros de 10 (10 minutes)

### Narrative

The purpose of this How Many Do You See is for students to subitize or use grouping strategies to describe the images they see. When students look for ways to see and describe numbers as groups of tens and ones and connect this to two-digit numbers, they look for and make use of the base-ten structure (MP7).

### Launch

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

### Activity

• Display image.
• “Discutan con su pareja lo que 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

• “¿Cómo describimos la segunda imagen usando decenas y unidades? ¿Cuántas decenas ven? ¿Cuántas unidades?” // “How did we describe the second image using tens and ones? How many tens do you see? How many ones?” (Some people said they saw it as 3 tens and 5 ones.)
• “¿Cómo podemos describir la última imagen usando decenas y unidades?” // “How could we describe the last image using tens and ones?” (3 tens and 9 ones)
• “¿Cómo podemos escribir ecuaciones que vayan con la última imagen?” // “How could we write equations to go with the last image?” ($$35 + 4 = 39$$ or $$30 + 9 = 39$$)

## Activity 1: ¿Qué sumé? (20 minutes)

### Narrative

The purpose of this activity is for students to apply their place value understanding to add an amount of tens or ones to a two-digit number. Students also use place value reasoning to determine whether a number of tens or ones was added to a two-digit number. Throughout the activity, students explain how they add and how they determined the unknown addend with an emphasis on place value vocabulary (MP3, MP6).

MLR2 Collect and Display. Circulate, listen for and collect the language students use as they talk with their partners. On a visible display, record words and phrases such as: tens, ones, sum, equation, starting number, secret number. Invite students to borrow language from the display as needed, and update it throughout the lesson.
Representation: Internalize Comprehension. Synthesis: Invite students to identify which details were most important to solve the problem. Display the sentence frame, “La próxima vez que sume un número de dos dígitos y un número de un dígito, prestaré atención a . . .” // “The next time I add a two-digit and one-digit number, I will pay attention to . . . .“
Supports accessibility for: Conceptual Processing, Organization

### Required Materials

Materials to Gather

### Launch

• Groups of 2
• Give each group a set of number cards and a paper clip. Give students access to connecting cubes in towers of 10 and singles.
• “Saquen las tarjetas de números del 0, 6, 7, 8, 9 y 10 y pónganlas aparte” // “Remove the 0, 6, 7, 8, 9 and 10 from the number cards.”
• “Vamos a jugar un juego en el que deben descifrar el número que su pareja sumó. Juguemos una ronda juntos. Todos ustedes son el compañero A y yo soy el compañero B” // “We are going to play a game where you must figure out the number your partner added. Let’s play a round together. All of you are partner A and I am partner B.”
• Invite a student to spin.
• “La ruleta paró en (43). Voy a tomar una tarjeta de número y voy a decidir si sumo esas unidades o esas decenas. Voy a decir la suma en voz alta” // “You spun (43). I will draw a number card and decide whether to add that many ones or that many tens. I will say the sum aloud.”
• “La suma es (93). ¿Qué número sumé? Hablen con su pareja. Prepárense para explicar cómo lo saben” // “The sum is (93). What number did I add? Talk with your partner. Be ready to explain how you know.” (You added 50. In order to get from 43 to 93 you add 5 tens. 53, 63, 73, 83, 93.)
• 1 minute: partner discussion
• Share responses.

### Activity

• “Ahora van a jugar con su pareja. En cada ronda, decidan si van a sumar decenas o unidades, y miren si su pareja puede adivinar lo que sumaron” // “Now you will play with your partner. For each round, decide whether you will add tens or ones and see if your partner can guess what you added.”
• 15 minutes: partner work time
• As students work, consider asking:
• “¿Cómo escogieron si sumar decenas o sumar unidades?” // “How did you choose to add tens or ones?”
• “¿Cómo encontraron el número que su pareja sumó?” // “How did you determine the number your partner added?”

### Student Facing

• Compañero A: gira la ruleta para obtener el número inicial.

• Compañero B: toma una tarjeta de números. No se la muestres a tu pareja. Escoge si le sumas esa cantidad de unidades o de decenas a tu número inicial. Asegúrate de no pasarte de 100. Cuéntale a tu pareja la suma que obtuviste.
• Compañero A: cuéntale a tu pareja que número crees que sumó y explica cómo pensaste.
• Intercambien roles y repitan lo anterior.

### Activity Synthesis

• “El compañero de Priya hizo girar la ruleta y esta cayó en 34. Priya escogió un 5. Si ella quiere sumar 5 unidades, ¿cómo puede encontrar la suma?” // “Priya’s partner landed on 34 on the spinner. Priya picked a 5. If she wants to add 5 ones, how could she find the sum?“ (She could count on. 35, 36, 37, 38, 39. She could add 5 more ones to the 4 ones in 34. 4 + 5 = 9 so its 39.)
• “¿Cómo puede encontrar la suma si quiere sumar 5 decenas?” // “How can she find the sum if she wants to add 5 tens?“ (She could count on by tens. 44, 54, 64, 74, 84. She could add 3 tens and 5 tens and get 8 tens.)

## Activity 2: Sumemos decenas o unidades (15 minutes)

### Narrative

In this activity, students add a one-digit number or a multiple of 10 and a two-digit number, without composing a ten. The order of the problems encourages students to analyze the difference between adding ones or tens (adding 5 or adding 50), which builds on the previous activity. Students rely on methods that they have learned such as counting on or using known facts to add. In the synthesis, students may say they notice that only the digit in the ones place of a two-digit number changes when they add a one-digit number to it. While this statement is true about the numbers in these problems, it will not be true when students add in future work. It may be helpful to record this conjecture on chart paper and revisit it again in future lessons to allow students an opportunity to explain whether or not it is always true.

### Launch

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.

### Activity

• 7 minutes: independent work time
• 3 minutes: partner discussion

### Student Facing

Encuentra el número que hace que la ecuación sea verdadera.

1. $$43 + 5 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
2. $$43 + 50 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
1. $$51 + 3 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
2. $$51 + 30 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
1. $$2 + 75= \boxed{\phantom{\frac{aaai}{aaai}}}$$
2. $$20 + 75 = \boxed{\phantom{\frac{aaai}{aaai}}}$$
1. $$93 + 6 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

Muestra cómo pensaste. Usa dibujos, números o palabras.

2. $$60 +28 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

Muestra cómo pensaste. Usa dibujos, números o palabras.

3. $$5 + 74 = \boxed{\phantom{\frac{aaai}{aaai}}}$$

Muestra cómo pensaste. Usa dibujos, números o palabras.

### Student Response

If students fill in both equations with the same number, consider asking:

• “En cada caso, ¿cómo encontraste el número que hace que la ecuación sea verdadera?” // “How did you find the number that makes each equation true?”
• “¿Cómo se vería cada expresión si usáramos cubos encajables? ¿Habría el mismo número de cubos?” // “How would each expression look with connecting cubes? Would there be the same number of cubes?”

### Activity Synthesis

• Display the first three problems.
• “¿Qué observaron sobre las ecuaciones y las sumas?” // “What did you notice about the equations and the sums?” (It was like adding the same number, just to a different place. When I add $$43 + 5$$, I only added the numbers in the ones place. When I add $$43 + 50$$, I added 5 tens and 0 ones to 43. The number in the ones place stayed the same.)

## Lesson Synthesis

### Lesson Synthesis

“Hoy sumamos decenas o unidades a números de dos dígitos. Mai y Andre sumaron 4 + 45. Mai dice que la suma es 85. Andre dice que la suma es 49. ¿Con quién están de acuerdo? ¿Por qué están de acuerdo con esa persona?” // “Today we added tens or ones to two-digit numbers. Mai and Andre added 4 + 45. Mai says the sum is 85. Andre says the sum is 49. Who do you agree with? Why do you agree with them?”(Mai added the 4 to the 4 tens in 45 to get 85. Andre added the 4 to the 5 ones in 45 to get 49. I agree with Andre, because 4 means 4 ones so you have to add the 4 to the ones. Mai added 4 tens which is 40.)