This Number Talk encourages students to use what they know about the meaning of fractions and about properties of operations to mentally relate fractions that are equivalent to whole numbers.
Launch
Display one fraction.
“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 answers and strategies.
Keep fractions and work displayed.
Repeat with each fraction.
En cada caso, encuentra el número entero que es equivalente a la fracción.
Student Response
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Advancing Student Thinking
Activity Synthesis
“¿Cómo les ayudaron las primeras fracciones a encontrar el número entero en el caso de la última fracción?” // “How did the earlier fractions help you find the whole number for the last fraction?”
Consider asking:
“¿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?”
Activity 1
Standards Alignment
Building On
Addressing
3.NF.A.3
Explain equivalence of fractions in special cases, and compare fractions by reasoning about their size.
The purpose of this activity is for students to analyze pairs of fractions to determine if they are equivalent. Students may use any representation that makes sense to them.
Monitor for and select to share in the Activity Synthesis students who used the following approaches to determine if and are equivalent:
Show that the fractions are not the same size, by drawing a diagram or by using fraction strips.
Show that the fractions are not at the same location on the number line.
Reason that since both fractions represent a different number of sixths, they cannot be equivalent.
The approaches are sequenced from more concrete to more abstract reasoning to help students make sense of the different ways they may compare fractions with the same numerator, or the same denominator, throughout the section. Monitor for the same approaches as students determine if and are equivalent, and invite students to connect and compare their representations if there is time. Aim to elicit both key mathematical ideas and a variety of student voices, especially students who haven't shared recently.
Launch
Groups of 2
“En cada caso, decidan si las dos fracciones son equivalentes y muestren cómo pensaron. Pueden usar cualquier representación que tenga sentido para ustedes” // “Decide if these pairs of fractions are equivalent and show your thinking for each one. You can use any representation that makes sense to you.”
Activity
5–8 minutes: independent work time
“Compartan sus ideas con su compañero” // “Share your ideas with your partner.”
2–3 minutes: partner discussion
As you monitor for the approaches listed in the Activity Narrative, consider asking:
“¿Qué identificaste sobre estas fracciones?” // “What did you notice about these fractions?”
“¿Cómo te ayuda tu diagrama a mostrar que las fracciones son o no son equivalentes?” // “How does your diagram help you prove whether or not they are equivalent?”
¿Estas fracciones son equivalentes? Muestra cómo pensaste. Usa diagramas, símbolos u otras representaciones.
y
y
y
Activity Synthesis
Invite previously selected students to share in the given order. Record or display their work for all to see.
Connect students’ approaches to the learning goal by asking:
“Estas son maneras distintas de decidir si y son equivalentes, ¿pero en qué se parecen?” // “These are different ways of thinking about whether and are equivalent, but how are they the same?” (All show they are not equivalent. The diagram and the number line show both fractions.)
“¿Cómo se mostró en cada representación que y no son equivalentes?” // “How did each representation show that and are not equivalent?” (In the diagram, you can see that has more space shaded. On the number line, they are not at the same location.)
If there is additional time, invite previously selected students to share their approaches for and .
Activity 2
Standards Alignment
Building On
Addressing
3.NF.A.3.d
Compare two fractions with the same numerator or the same denominator by reasoning about their size. Recognize that comparisons are valid only when the two fractions refer to the same whole. Record the results of comparisons with the symbols , =, or , and justify the conclusions, e.g., by using a visual fraction model.
The purpose of this activity is for students to recognize that fraction comparisons are valid only when they refer to the same-size whole. Previously, students analyzed pairs of fractions to determine if they were equivalent. In doing so, they likely used comparison language, such as “larger than” or “smaller than” or “greater than” or “less than.” In this activity, students encounter a pair of fractions they saw earlier ( and ) and compare them more explicitly. The student work in this activity uses the number line, but this might also come up with student-drawn diagrams.
In order to interpret Lin’s argument that is greater than , students need to articulate the meaning of fractions and highlight the fact that the two wholes Lin is comparing are not equal (MP6).
MLR8 Discussion Supports. Synthesis: Revoice student ideas to demonstrate and amplify mathematical language use. For example, revoice the student statement "las rectas numéricas son diferentes" // “the number lines are different” as "el tamaño de la unidad de 0 a 1 es diferente" // “the size of the whole from 0 to 1 is different.” Advances: Speaking, Representing
Launch
Groups of 2
“Han y Lin comparan y , de la misma manera en que ustedes lo hicieron. Tómense un minuto para examinar su trabajo” // “Han and Lin are comparing and , the same way you did. Take a minute to look at their work.”
1 minute: quiet think time
Activity Synthesis
Select previously identified students to share how Han and Lin could make different comparison statements for the same fractions.
“Cuando comparamos fracciones, es importante recordar que esas fracciones deben hacer referencia a una unidad del mismo tamaño” // “It is important to remember when we are comparing fractions that those fractions need to refer to the same-size whole.”
“Cuando la unidad de 0 a 1 es del mismo tamaño, podemos ver que es menor que ” // “When the whole from 0 to 1 is the same size, we can see that is less than .”
“Esto es cierto independientemente de que dibujemos una recta numérica, usemos tiras de fracciones o dibujemos un diagrama” // “This is true whether we are drawing a number line, using fraction strips, or drawing a diagram.”
Consider asking, “¿Qué entendieron Lin y Han sobre representar fracciones en una recta numérica?” // "What did both Lin and Han understand about representing fractions on a number line?” (The number lines need to be partitioned into equal parts. The denominator tells us the number of parts. The numerator tells us how many parts to count to locate a point. Points farther to the right are greater than those to the left.)
Lesson Synthesis
“Hoy estudiamos parejas de fracciones para saber si eran equivalentes o no. ¿Cómo decidieron si dos fracciones eran equivalentes?” // “Today we studied pairs of fractions to see if they were equivalent or not. How did you decide if two fractions were equivalent?” (Drew diagrams to see if the parts that represent the fractions were the same size. Represented the fractions on number lines to see if they were at the same location.)
“Si las fracciones no eran equivalentes, esto significa que una de las fracciones era mayor que la otra y una de las fracciones era menor que la otra. Vamos a aprender más sobre esto en otras lecciones” // “If the fractions were not equivalent, it means that one of the fractions was greater than the other, and one of the fractions was less than the other. We'll learn more about this in future lessons.”
Draw two number lines (or diagrams) with different lengths (or areas) representing 1 whole. Partition each whole into 3 parts.
“¿Cuál podría ser un problema si comparamos y usando estas rectas numéricas (o diagramas)?” // “What might be a problem with comparing and , using these number lines (or diagrams)?” (The 1 wholes are not the same size, so we can’t use the number lines (or diagrams) to compare the fractions.)
Standards Alignment
Building On
Addressing
3.NF.A.3.c
Express whole numbers as fractions, and recognize fractions that are equivalent to whole numbers. Examples: Express in the form ; recognize that ; locate and at the same point of a number line diagram.
If students determine whether the fractions are equivalent, without showing their thinking, consider asking:
“¿Cómo decidiste si ___ y ___ son equivalentes?” // “How did you decide whether __ and __ are equivalent?”
“¿Cómo puedes usar tiras de fracciones o diagramas para mostrar cómo pensaste?” // “How could you use fraction strips or diagrams to show your thinking?”
Activity
“Hablen con su compañero sobre cómo pudieron Han y Lin obtener resultados diferentes” // “Talk with your partner about how Han and Lin could get different results.”
2–3 minutes: partner discussion
Monitor for students who notice that the whole is different in Lin’s number lines, which makes her think that is greater.
Han dice que es menor que . Este es su trabajo.
Lin dice que es mayor que . Este es su trabajo.
¿Por qué Han y Lin hacen afirmaciones de comparación diferentes sobre las mismas fracciones?