PLENTIFUL POMEGRANATES [DAY 3]
SUBTRACTION STRATEGY: PLACE VALUE TO ALGORITHM
Explore efficient strategies to subtract values within 50
Intentionality
Spark Curiosity
Fuel Sensemaking
During Moves
Student Approaches
Next Moves
Consolidation
Reflect and Consolidation Prompts
Resources & Downloads
Educator Discussion Area
Intentionality & Unit Overview
Length of Unit: 5 Days
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Students will solve a subtraction question using the takeaway strategy of place value leading to a discussion about the standard algorithm.
Intentionality…
Students will solve a subtraction question using the takeaway strategy of place value leading to a discussion about the standard algorithm.
Some of the big ideas that may emerge through this task include:
- Numbers can be decomposed by separating a whole into two or more parts
- Exchanging or regrouping occurs when the subtrahend in a place value is bigger than the minuend
- Subtraction names the missing part in terms of the whole
- Different subtraction situations will elicit different strategies
- Number relationships provide the foundation for strategies to help students remember basic facts
- Subtraction can be used in either takeaway, comparison or missing addend situations. This task will explore the takeaway method.
- Models can be used to connect concrete to abstract
Spark Curiosity
What Do You Notice? What Do You Wonder?
Show students the following video:
Then, ask students:
What do you notice?
What do you wonder?
Give students about 30-60 seconds to do a rapid write on a piece of paper or silent individual think time.
Replaying the video can be helpful here if appropriate.
Then, ask students to share with their neighbours for another 60 seconds.
Finally, allow students to individually share with the entire group. Be sure to write down these noticings and wonderings on the blackboard/whiteboard, chart paper, or some other way that is visible to all. This helps students to see the thinking of their classmates and ensures each student that their voice is acknowledged and appreciated. Adding student names or initials next to their notice/wonder is one way to acknowledge their participation and can motivate others to join in.
Some noticings and wonderings that may come up:
- I notice the apple is cut
- I notice there are seeds in the orange
- I notice the pomegranate has lots of seeds
- I wonder what the “ball” inside the avocado is called?
- I wonder how many seeds are in an orange
- And many more
Estimation: Prompt
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While Students are Estimating:
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Estimation: Reveal
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Fuel Sense-making
Crafting A Productive Struggle: Prompt
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During Moves
While Students Are Productively Struggling…
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Student Approaches
Student Approach #1: Using a Tool to Direct Model and Count All
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Student Approach #2: Counting All with a Drawing
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Student Approach #3: Open Number Line to decompose the subtrahend by taking away tens then counting back
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Student Approach 4: Open Number Line to decompose the subtrahend by taking away tens then ones
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Student Approach 5: Place Value/ Standard Algorithm with base ten manipulatives
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Student Approach 6: Place Value/ Standard Algorithm
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Next Moves
Reveal #1:
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Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.Consolidation
Reflect and Consolidation Prompts
After the reveal, check back to student responses. The purpose here is to reflect on student reasoning, not on celebrating who was closest.
Provide students with an opportunity to reflect on their learning by offering these consolidation prompts to be completed independently and then discussed as a class.
Consolidation Prompt #1:
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Consolidation Prompt #2:
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Consolidation Prompt #3:
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We suggest collecting this reflection as an additional opportunity to engage in the formative assessment process to inform next steps for individual students as well as how the whole class will proceed.
Resources & Downloads
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Printable Lesson Plan PDF
Videos, Images & Media Files
Apple Keynote Presentation
Powerpoint Presentation
Printable Consolidation Prompts
Educator Discussion Area
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