The purpose of this Estimation Exploration is for students to apply their understanding of dividing a whole number by a fraction from previous lessons. The dividend in this expression is much larger than those that students have previously worked with to encourage students to use multiplication to estimate.
Launch
Groups of 2
Display the expression.
“What is an estimate that’s too high? Too low? About right?”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
1 minute: partner discussion
Record responses.
Student Task Statement
Record an estimate that is:
too low
about right
too high
Student Response
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Advancing Student Thinking
Activity Synthesis
“How do you know the value of is less than 500?" (It's less than and that's 500)
Activity 1
20 mins
Greater Than or Less Than 1
Standards Alignment
Building On
Addressing
5.NF.B.7
Apply and extend previous understandings of division to divide unit fractions by whole numbers and whole numbers by unit fractions.Students able to multiply fractions in general can develop strategies to divide fractions in general, by reasoning about the relationship between multiplication and division. But division of a fraction by a fraction is not a requirement at this grade.
The purpose of this activity is for students to reason about the size of quotients, involving a unit fraction and a whole number, by carefully analyzing the relative sizes of the dividend and divisor rather than finding the value of the expressions. As students work, listen for the language they use to explain why they think the value of an expression is greater than or less than 1. Highlight the language during the Activity Synthesis. When students explain to each other how they decided whether a quotient is greater than 1 or less than 1 they construct viable arguments (MP3).
This activity uses MLR1 Stronger and Clearer Each Time. Advances: Reading, Writing.
Engagement: Provide Access by Recruiting Interest. Synthesis: Optimize meaning and value. Invite students to share if a previously selected expression is less than or greater than one and how they determined the value of the expression (display of their work on a problem, strategy they used, verbal explanation with a classmate who missed the lesson). Supports accessibility for: Attention, Conceptual Processing, Memory
Launch
Groups of 2
Activity
1–2 minutes: quiet think time
5–8 minutes: partner work time
Student Task Statement
Without calculating the value of the expressions, write each expression under the correct category.
The value of the expression is less than 1.
The value of the expression is greater than 1.
Explain your strategy for determining whether a quotient is less than 1 or greater than 1.
Activity Synthesis
MLR1 Stronger and Clearer Each Time
“Share your explanation for determining whether a quotient is less than or greater than 1 with your partner. Take turns being the speaker and the listener. If you are the speaker, share your ideas and writing so far. If you are the listener, ask questions and give feedback to help your partner improve their work.”
3–5 minutes: structured partner discussion.
Repeat with 2–3 different partners.
If needed, display question starters and prompts for feedback.
“Can you give an example to help show . . . ?”
“How can you use the words divisor and dividend in your explanation?”
“Revise your initial draft based on the feedback you got from your partners.”
2–3 minutes: independent work time
Activity 2
15 mins
Estimate and Divide
Standards Alignment
Building On
Addressing
5.NF.B.7
Apply and extend previous understandings of division to divide unit fractions by whole numbers and whole numbers by unit fractions.Students able to multiply fractions in general can develop strategies to divide fractions in general, by reasoning about the relationship between multiplication and division. But division of a fraction by a fraction is not a requirement at this grade.
The purpose of this activity is for students to order the quotients from the previous activity from least to greatest, without calculating. The quotients of a whole number by a unit fraction have the same dividend so students reason that the expression with the smallest unit fraction divisor represents the largest quotient. In the same way, the quotients of a unit fraction by a whole number all have the same divisor so the expression with the largest unit fraction dividend is the largest.
Launch
Groups of 2
Activity
5 minutes: independent work time
5 minutes: partner discussion
Monitor for students who:
Explain that the greatest quotient is because it represents the largest number of pieces.
Explain that the smallest quotient is because it represents the smallest sized pieces.
Change their response after the partner discussion.
Student Task Statement
Without calculating the value of the expressions, put the expressions in order from least to greatest.
Choose 2 expressions and find the value of the expressions.
Student Response
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Advancing Student Thinking
If students confuse the strategies for dividing a whole number by a unit fraction with dividing a unit fraction by a whole number, consider asking:
“Can you explain how you put the expressions in the order?”
Refer to one of the expressions. “Will the quotient be greater than or less than the dividend?”
Activity Synthesis
Ask previously selected students to explain their reasoning.
“What was challenging about this activity?” (It was hard to explain without finding any values.)
“How did reasoning about the order of the expressions help you find the value of 2 of the expressions?” (I knew the value was going to be a unit fraction [or whole number].)
Lesson Synthesis
Display:
“What do we know about the value of this expression if the number in the box is a whole number?” (It is going to be greater than 25. It is going to be a multiple of 25.)
Display:
“What do we know about the value of this expression if the number in the box is a whole number?” (It is going to be a unit fraction. The denominator is going to be a multiple of 25.)
Student Section Summary
We learned to divide with whole numbers and unit fractions. First, we used diagrams to solve problems involving division of a unit fraction by whole numbers.
Example:
Diagram A shows equals . We find the size of one part if is split into 4 equal parts.
Diagram A
Then we noticed the relationship between division and multiplication.
For Diagram A, we know that because .
Next, we used diagrams to solve problems involving division of whole numbers by unit fractions. We also wrote equations to represent these problems.
Example:
Diagram B shows that if a strip of paper 2 feet long is cut into foot pieces, there will be 12 pieces. Therefore, because we are finding how many -size pieces are the same length as 2.
Diagram B
Finally, we noticed patterns when dividing whole numbers and unit fractions.
We noticed whole numbers divided by unit fractions were greater than 1.
Example:
The value of is greater than 1. The number of -size pieces with length 12 (or any whole number) is greater than 1.
We also noticed unit fractions divided by whole numbers were less than 1.
Example:
The value of is less than 1. When a whole number less than 1 is divided into many pieces, each piece is less than 1.
Have feedback on the curriculum?
Help us improve by sharing suggestions or reporting issues.
Interpret division of a whole number by a unit fraction, and compute such quotients. For example, create a story context for , and use a visual fraction model to show the quotient. Use the relationship between multiplication and division to explain that because .