Task Teacher Guide
Be sure to read the teacher guide prior to running the task. When you’re ready to run the task, use the tabs at the top of the page to navigate through the lesson.
In This Task…
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
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?
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…
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Student Approach #1: Concrete & Part Whole Model
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Student Approach #2: Ten Frames & Subitizing
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Student Approach #3: Number Path & Counting Backwards
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Next Moves
Consolidation
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Purposeful Practice
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
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.
Download Editable/Printable Handout
Become a member to access purposeful practice to display via your projector/TV, download the PDF to upload to your LMS and/or print for students to have a physical copy
Resources and Downloads
Lesson Tip Sheet
Download the lesson plan in PDF format so you can keep it handy and share with colleagues.
Videos & Images
Download the videos, images, and related media files to your computer to avoid streaming.
Keynote Slides
Download in Apple Keynote format to avoid streaming video and run the lesson smoothly.
PowerPoint Slides
Download in Microsoft PowerPoint format to avoid streaming video and run the lesson smoothly.
Printable Handout
Download/edit the handout so you can keep it handy and share with colleagues.
Explore The Entire Unit of Study
This Make Math Moments Task was designed to spark curiosity for a multi-day unit of study with built in purposeful practice, and extensions to elicit and emerge mathematical models and strategies.
Click the links at the top of this task to head to the other related lessons created for this unit of study.
How many?
10 – 1
…
10 – 9
…
15 – 12
…
15 – 3
…
17 – 4
…
17 – 13
Prompt:
There were 25 gummy worms in the jar.
Now there are only 14 left.
How many gummy worms were eaten?
1. Cookies Prompt
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
1. Cookies Image
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
2. Trip To The Store: Prompt
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
2. Trip To The Store: Image
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
3. T.V. Time
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
4. Write…
Login/Join to access the entire Teacher Guide, downloadable slide decks and printable handouts for this lesson and all problem based units.
Download Editable/Printable Handout
Become a member to access purposeful practice to display via your projector/TV, download the PDF to upload to your LMS and/or print for students to have a physical copy