# Lesson 7

Dividamos para multiplicar fracciones unitarias

## Warm-up: Exploración de estimación: Recta numérica (10 minutes)

### Narrative

The purpose of this Estimation Exploration is for students to practice estimating a given length on a number line. Students are given the length of a longer segment as a point of reference and apply their understanding of equal parts to the number line to estimate a shorter length.

### Launch

• Groups of 2
• Display the image.
• “¿Qué número podría ir en el cuadro? ¿Qué estimación sería muy alta?, ¿muy baja?, ¿razonable?” // “What number could go in the box? What is an estimate that’s too high? Too low? About right?”
• 1 minute: quiet think time

### Activity

• “Discutan con su compañero cómo pensaron” // “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.

### Student Facing

Escribe en el cuadro el número que corresponde a la marca en la recta numérica.

Escribe una estimación que sea:

muy baja razonable muy alta
$$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$ $$\phantom{\hspace{2.5cm} \\ \hspace{2.5cm}}$$

### Student Response

If students do not explain why the number in the box is going to be less than half of 5, ask them to identify the approximate location of the numbers 1, 2, 3, and 4 on the number line.

### Activity Synthesis

• “¿El número que va en el cuadro es menor o mayor que la mitad de 5? ¿Cómo lo saben?” // “Is the number that goes in the box more or less than half of 5? How do you know?” (Less, since it is less than half the way to 5.)
• “¿Cómo les ayuda esto a estimar el valor?” // “How does this help you estimate the value?” (I know half of 5 is $$2 \frac{1}{2}$$,  so it is less than that.)
• Optional: Reveal the actual value and add it to the display.

## Activity 1: ¿Qué distancia corrieron? (20 minutes)

### Narrative

The purpose of this activity is for students to use the structure they noticed in the previous lesson to solve real world problems in which a whole number is multiplied by a unit fraction. Students may use a variety of strategies to solve these problems. They may relate the situations to multiplication of a whole number by a fraction or division of two whole numbers. During the synthesis, connect the different interpretations of the situations.

Students share their different representations and expressions and explain to each other how they relate to the running situation (MP3).

This activity uses MLR7 Compare and Connect. Advances: Representing, Conversing.

• Groups of 2

### Activity

• 1–2 minutes: independent think time
• 5 minutes: partner work time
• Monitor for:
• students who draw diagrams including continuous number line representations and discrete rectangular representations like the ones used in earlier lessons
• students who use different multiplication or division expressions
• students who write their final answer as a fraction or as a mixed number

MLR7 Compare and Connect

• “Creen una presentación visual que muestre lo que pensaron al hacer el segundo problema. Incluyan detalles, como notas, diagramas, dibujos, etc., para ayudar a los demás a entender cómo pensaron” // “Create a visual display that shows your thinking about the second problem. You may want to include details such as notes, diagrams, drawings, etc., to help others understand your thinking.”
• 5–7 minutes: gallery walk
• “¿En qué se parecen y en qué son diferentes las distintas formas de resolver el problema?” // “What is the same and what is different between the different approaches to solving the problem?”
• 30 seconds quiet think time
• 1 minute: partner discussion
• “¿Alguien quiere hacer una pregunta sobre alguna estrategia o alguna solución?” // “Does anyone have a question they would like to ask about a strategy or solution?”
• Consider asking students if they would like to revise their work before the synthesis.

### Student Facing

Resuelve cada problema. Si te ayuda, dibuja un diagrama.

1. Mai corrió $$\frac{1}{4}$$ del total de un camino que mide 9 millas de largo. ¿Qué distancia corrió Mai?
2. Han corrió $$\frac{1}{4}$$ del total de un camino que mide 7 millas de largo. ¿Qué distancia corrió Han?

### Student Response

If students do not know how to figure out what $$\frac{1}{4}$$ of 7 or 9 miles is, ask them to figure out how far Mai would have run if she ran $$\frac{1}{4}$$ of an 8 mile road.

### Activity Synthesis

• Ask previously selected students to share their solutions.
• “¿Qué expresiones representan la distancia que corrió Han?” // “What are some expressions that represent the distance Han ran?” ($$7 \div 4$$, $$1 \frac{3}{4}$$, $$\frac{7}{4}$$, $$\frac{1}{4}\times7$$)
• “¿Cómo estas expresiones representan la distancia que corrió Han?” // “How does each of these expressions represent the distance Han ran?” (He ran $$\frac{1}{4}$$ of 7 miles and we can write that as $$\frac{1}{4} \times 7$$. We can figure out how many miles that is if we divide 7 into 4 equal parts. That’s $$7\div4$$ or $$\frac{7}{4}$$ or $$1\frac{3}{4}$$.)

## Activity 2: ¿Cuáles describen la situación? (15 minutes)

### Narrative

The purpose of this activity is to match different expressions and diagrams with one situation. Some students may match the expressions, diagrams, and situation by finding the solution to the problem and the value of each expression. Some may match the representations without finding the value of the expressions. During the activity synthesis, highlight how the different expressions relate both to the situation and to the diagrams, and connect the relationships to the meaning of the expressions and diagrams.

Students reason abstractly and quantitatively (MP2) when they relate the story to the diagrams and expressions. All of the diagrams and expressions involve the same set of numbers so students need to carefully analyze the numbers in the story, the diagrams, and the expressions in order to choose the correct matches.

MLR8 Discussion Supports. Students should take turns finding a match and explaining their reasoning. Display the following sentence frames for all to see: “Observé que _____, entonces asocié . . .” // “I noticed _____ , so I matched . . .” and “_____ y _____ se parecen/son diferentes porque . . .” // “_____ and _____ are the same/different because . . . .” Encourage students to challenge each other when they disagree.
Engagement: Provide Access by Recruiting Interest. Synthesis: Invite students to generate a list of additional situations the images could represent that connect to their personal backgrounds and interests.
Supports accessibility for: Attention, Conceptual Processing

### Required Materials

Materials to Copy

• Match the Situation

### Required Preparation

• Create a set of cards from the blackline master for each group of 2.

• Groups of 2

### Activity

• 8 minutes: partner work time
• Monitor for students who match the expressions and diagrams by thinking about the meaning in each case.

### Student Facing

Han, Lin, Kiran y Jada corrieron juntos una carrera de relevos de 3 millas. Todos corrieron la misma distancia.

1. Encuentra las expresiones y los diagramas que corresponden a esta situación. Prepárate para explicar tu razonamiento.
2. ¿Qué distancia corrió cada persona?

### Student Response

If students do not match the diagrams and expressions correctly, ask students to explain how each diagram and expression represents each part of the situation.

### Activity Synthesis

• Display cards J and K.
• “¿En qué se parecen estos diagramas? ¿En qué son diferentes?” // “How are these diagrams the same? How are they different?” (They both show $$\frac{3}{4}$$ or $$3 \div 4$$. The first one shows $$\frac{1}{4}$$ of each whole. In the second one, the shaded parts are all together, so they show $$\frac{3}{4}$$ of a single whole.)
• Display the expression: $$\frac{1}{4} \times 3$$.
• “¿Cómo se relaciona esta expresión con la situación?” // “How does this expression relate to the situation?” (The race is 3 miles long and each person will run $$\frac{1}{4}$$ of the race.)
• “¿De qué manera los diagramas representan la expresión?” // “How do the diagrams represent the expression?” (In the first diagram $$\frac{1}{4}$$ of each whole is shaded. It is harder to see in the second diagram because I can't tell that the shaded parts are $$\frac{1}{4}$$ of the 3 rectangles.)
• “¿Cómo podemos adaptar la tarjeta K para mostrar que hay 4 secciones iguales de $$\frac{3}{4}$$?” // “How can we adapt card K to show there are 4 equal sections of $$\frac{3}{4}$$?” (We could show the sections.)
• Mark card K to show the 4 equal sections of $$\frac{3}{4}$$. For example, use different colors to show the other 3 sections of $$\frac{3}{4}$$.

## Lesson Synthesis

### Lesson Synthesis

“Hoy aprendimos cómo encontrar fracciones de un número entero” // “Today we learned how to find fractions of a whole number.”

“¿Qué significa correr $$\frac{1}{4}$$ de un camino de 10 millas?” // “What does it mean to run $$\frac{1}{4}$$ of a 10 mile road?” (If you break up the 10 miles into 4 equal pieces, you ran 1 of those pieces.)

“¿Qué expresiones pueden escribir para representar $$\frac{1}{4}$$ de 10?” // “What expressions can you write to represent $$\frac{1}{4}$$ of 10? ($$\frac{1}{4} \times 10$$, $$10 \div 4$$, $$10 \times \frac{1}{4}$$)

“¿Qué expresión les ayuda a calcular cuánto es $$\frac{1}{4}$$ de 10 millas?” // “Which expression helps you calculate how far $$\frac{1}{4}$$ of 10 miles is?” ( $$10 \div 4$$ because I know it is $$\frac{10}{4}$$.)