# Lesson 1

## Warm-up: ¿Qué sabes sobre la medición? (10 minutes)

### Narrative

The purpose of this warm-up is to invite students to share what they know about measuring. Students measured the length of objects in grade 1 using non-standard units such as paper clips and tiles and may also have experience measuring length outside of school. This warm-up allows teachers to hear the language students use to talk about measurement and what attributes of objects they attend to in order to measure.

### Launch

• “¿Qué saben sobre la medición?” // “What do you know about measuring?”
• 1 minute: quiet think time

### Activity

• Record responses.

### Student Facing

¿Qué sabes sobre la medición?

### Activity Synthesis

• “¿Qué significa medir?” // “What does it mean to measure?” (To find out how long something is.)
• “Vamos a seguir pensando en lo que sabemos sobre la medición y vamos a aprender más sobre ella en las próximas actividades” // “We are going to continue thinking about what we know and learn more about measuring in our upcoming activities.”

## Activity 1: La mascota de Priya (15 minutes)

### Narrative

The purpose of this activity is to emphasize the importance of identifying the length of a unit when measuring (MP6). Students work in groups to measure the same length of string using straws. Students find and report measurements of different lengths because they are provided with straws of different lengths. In the synthesis, students discuss that although the same length of string was measured, the measurements are different, because different length units were used. This sets students up to discuss what happens when everyone uses the same length unit in the next activity.

Straws may be replaced by pipe-cleaners or other rigid objects that can be cut to the specified lengths.

This activity uses MLR8 Discussion Supports. Advances: Listening, Representing

### Required Materials

Materials to Gather

### Required Preparation

• Create a 40-cm length of string or ribbon for each group of 23.
• Create five 10-cm length straws for half of the groups of 23.
• Create ten 5-cm length straws for half of the groups of 23.

### Launch

• Groups of 2–3
• Give each group a set of straws (some groups get 10-cm long straws and others get 5-cm long straws) and a string that measures 40 cm long.
• Display the image.
• “¿Qué saben sobre este animal? ¿Qué podrían medir?” // “What do you know about this animal? What could you measure?”
• 30 seconds: quiet think time
• 1 minute: partner discussion
• Share responses.

### Activity

• “Priya tiene una iguana como mascota. Ella piensa que la iguana puede estar lista para un nuevo terrario y quiere saber qué tan larga es la iguana” // “Priya has a pet iguana. She thinks he may be ready for a new cage and wants to know how long he is.”
• “Primero, Priya usó un pedazo de cuerda para medir la longitud de su mascota. Ella empezó desde la cabeza de la iguana y extendió la cuerda hasta su cola. Priya cortó la cuerda para que fuera de la misma longitud que su iguana” // “First, Priya used a piece of string to measure the length of her pet. She started at the iguana’s head and stretched it all the way to its tail. She cut the string so it was the same length as her iguana.”

MLR8 Discussion Supports

• Use gestures to emphasize how Priya might measure the length of the iguana. For example, when describing how Priya uses the string, use your hands to emphasize one end of the string at the head, pull the string taut, and emphasize the end at the tail.
• “Cada grupo tiene un pedazo de cuerda que tiene la misma longitud que la cuerda de Priya” // “Each group has a piece of string that is the same length as Priya’s string.”
• “Van a medir la cuerda de Priya usando las pajillas que están sobre sus mesas” // “You are going to measure Priya’s string using the straws at your tables.”
• 5 minutes: small-group work time
• As students work, monitor for students from each group (short straws and long straws) who line up the straws end to end with no gaps or overlaps to share their method in the synthesis.

### Student Facing

Usa pajillas para medir la cuerda que muestra qué tan larga es la iguana de Priya.

La iguana de Priya mide ____________ pajillas de largo.

### Student Response

If students leave gaps between straws or have straws overlapping, have them compare their measurements with another group who had straws of the same length. Consider asking:

• “¿Por qué piensas que tu número total de pajillas es diferente?” // “Why do you think your total number of straws is different?”
• “¿Cómo te aseguraste de medir toda la longitud de la cuerda?” // “How did you make sure the entire length of the string was measured?”

### Activity Synthesis

• “¿Qué tan larga es la cuerda de Priya?” // “How long is Priya’s string?”
• Record responses.
• “¿Por qué son diferentes nuestras medidas de la longitud?” // “Why are our length measurements different?” (Some groups maybe didn’t line up their straws correctly. Maybe the straws weren’t the same size.)
• 30 seconds: quiet think time
• 1 minutes: partner discussion
• Share responses.
• Invite previously identified students to demonstrate their measurements.
• “Ambos grupos empezaron desde el comienzo de la cuerda y alinearon pajillas sin dejar espacios ni superposiciones hasta llegar al final” // “Both of these groups started at the beginning of the string and lined up straws with no gaps or overlaps until they reached the end.”
• “¿Por qué las medidas son diferentes?” // “Why are the measurements different?” (The straws are different sizes. One group used short straws and one group used long straws.)
• “Las medidas son diferentes porque cada grupo usó diferentes unidades de longitud” // “The measurements are different because each group used different length units.”
• “Una unidad de longitud es la longitud del objeto que se usa para medir” // “A length unit is the length of the object you use to measure.”

## Activity 2: Usemos una unidad estándar (20 minutes)

### Narrative

The purpose of this activity is for students to understand why it is important to be precise about the length of the unit used to measure (MP6). All student groups use centimeter cubes to measure. After measuring, students compare their measurements with other groups. In the synthesis, they discuss why each group's measurement is the same, or nearly the same, after they measured with the cubes. Students are introduced to standard units, but do not need to use this term.

Representation: Internalize Comprehension. Invite students to identify which details were important to solve the problem in Activity 1. Display the sentence frame, “La próxima vez que queramos medir la longitud de un objeto, voy a fijarme en que la herramienta para medir esté alineada con el objeto desde su extremo. Debo asegurarme de que no haya espacio entre las unidades que uso para medir” // “The next time we want to measure the length of an object, I will pay attention to how I line up the measuring tool with the end of the object to be measured, and make sure there is no space between the measuring units.”
Supports accessibility for: Organization, Attention

### Required Materials

Materials to Gather

### Required Preparation

• Gather a connecting cube to display in the activity synthesis. Students will not need connecting cubes for this activity.

### Launch

• Groups of 2–3
• Give each group centimeter cubes.
• “En la actividad anterior, vimos por qué es importante usar la misma unidad de longitud para medir. Si usamos objetos como nuestra unidad de longitud, tenemos que estar todos de acuerdo en el tamaño de cada objeto” // “In the last activity, we saw why it’s important to use the same length unit to measure. If we use objects as our length unit, we need to all agree on the size of each object.”
• “Todos vamos a usar bloques en base diez para medir la cuerda de Priya. ¿Qué saben sobre el tamaño y la forma de estos bloques?” // “We are all going to use single base-ten blocks to measure Priya’s string. What do you know about the size and shape of these blocks?” (They are small. They are all the same size. They are cubes.)

### Activity

• “Su tarea es usar estos cubos para medir la longitud de la cuerda” // “Your job is to use these cubes to measure the length of the string.”
• 5 minutes: small-group work time
• 5 minutes: small-group discussion

### Student Facing

Usa los cubos para medir la cuerda de Priya.

1. La iguana de Priya mide ______ cubos de largo.
2. Compara tu medida con la de otro grupo.

### Activity Synthesis

• Share and record measurements.
• “¿Por qué las medidas de todos los grupos son la misma longitud o aproximadamente la misma longitud?” // “Why is every group's measurements the same, or closer to the same, length?” (They are the same because we all used the same length unit. We all used cubes that have the same length.)
• As needed, restate student responses when they say the cubes are “the same” to emphasize that the cubes have the same length.
• Display a centimeter cube and a connecting cube.
• “Si algunos grupos hubieran usado estos cubos y otros grupos hubieran usado cubos encajables, ¿habrían sido nuestras medidas la misma? ¿Por qué?” // “If some groups used these cubes and other groups used connecting cubes, would our measurements have been the same? Why?” (It would not be the same because the cubes are not the same length.)
• “Usar pajillas y cubos como unidades de longitud puede ser confuso porque hay pajillas y cubos de muchos tamaños diferentes” // “Straws and cubes can be confusing to use as length-units because they can be lots of different sizes.”
• “Hay unidades que las personas en todo el mundo usan para medir porque siempre tienen el mismo tamaño. Estas unidades se llaman ‘unidades estándar’” // “There are units that people around the world use to measure that always have the same size. They are called standard units.”

## Lesson Synthesis

### Lesson Synthesis

“Hoy medimos la longitud de una cuerda usando diferentes unidades. Usamos pajillas y cubos” // “Today, we measured a length of string using different units. We used straws and cubes.”

Display a centimeter cube.

“Los cubos que usamos hoy pueden llamarse ‘cubos de un centímetro’ porque la arista de cada cubo mide 1 centímetro de largo. Un centímetro es una unidad estándar de longitud en el sistema métrico de medidas” // “The cubes we used today can be called centimeter cubes because the edge of each cube is 1 centimeter long. A centimeter is a standard length unit in the metric measurement system.”

Display:

• Priya’s iguana is 40 cubes long.
• Priya’s iguana is 40 centimeter cubes long.

“¿Qué afirmación describe mejor la longitud de la iguana de Priya? Expliquen” // “Which sentence best describes the length of Priya’s iguana? Explain.”