GUMMY WORMS [DAY 4]
SUBTRACTION
Uncover the various subtraction structures including removal, conparison, missing, addend, and missing subtrahend.
Intentionality
Math Talk
Spark Curiosity
Fuel Sensemaking
During Moves
Student Approaches
Consolidation
Purposeful Practice
Resources & Downloads
Educator Discussion Area
Intentionality & Unit Overview
Length of Unit: 5 Days
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Students will explore a third subtraction structure: missing subtrahend.
Intentionality…
The purpose of the Day 4 activities is to reinforce key concepts from Day 3 and to explore a new subtraction structure; missing subtrahend. Students will engage in a math talk, investigate a new task and independently complete purposeful practice. Today’s learning serves to develop a deeper understanding of the following big ideas.
- Part-whole relations: Relationships between addition & subtraction.
- One-to-one correspondence.
- Measured and unmeasured comparison can be used to describe the relationship between two quantities
- One structure of subtraction is “removal”.
- One structure of subtraction is comparison (or difference).
- One structure of subtraction is “missing subtrahend”.
Math Talk
Related String of Problems
Through the following string or related problems, students might be encouraged to use a variety of strategies, depending on the numbers in the subtraction sentence. When the numbers are close together, students are likely to see this subtraction as “difference” and they may use a strategy such as “counting on”. When the subtrahend (the second number in the sentence) is significantly smaller the minuend (the first number), students may view this subtraction as “take away” or separate and are more likely to count back by ones and take jumps to friendly numbers. Consider modelling student thinking on a concrete number line or number path. Be sure to highlight the two different subtraction structures.
10 – 1
10 – 9
15 – 12
15 – 3
17 – 4
17 – 13
Spark Curiosity
Building On The Context Through Storytelling
Remind students of the context developed on Day 1 and 3. For today’s task, you might also consider bringing back your jar of gummy worms and explaining today’s context orally.
As you know, I had a jar that contained 25 gummy worms. When I came back this morning, there were only 14 gummy worms left in the jar. At some point last night, someone must’ve come in and helped themselves to some gummy worms. I am wondering how many they ate so that I can go to the store and replace them. Can you help me figure it out?
Fuel Sense-making
Crafting A Productive Struggle: Prompt
Share the prompt formally with students:
There were 25 gummy worms in the jar. Now there are only 14 left. How many gummy worms were eaten?
Facilitator Notes
In this task, students will have an opportunity to reason through a subtraction scenario. This particular problem is an example of the “missing subtrahend” subtraction structure. This task will allow students to apply a variety of strategies and models, while developing a deeper understanding of big ideas, specifically the following;
- Part-whole relations: Relationships between addition & subtraction. .
- One structure of subtraction is “missing subtrahend”.
During Moves
While Students Are Productively Struggling…
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Student Approaches
Student Approach #1: Concrete & Part Whole Model
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Student Approach #2: Ten Frames & Subitizing
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Student Approach #3: Number Path & Counting Backwards
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Consolidation
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Purposeful Practice
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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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