Task Teacher Guide
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In This Task…
Students will determine if a 20% decrease followed by a 20% increase results in no change in value, a decrease in value, or an increase in value.Â
Intentionality…
In this task, students will apply their understanding of percent to determine percentage increases and percentage decreases. Some of the big ideas that may emerge through this task include:
- Decreasing by a percentage will lower the original value.Â
- Increasing by a percentage will increase the original value.Â
- A percentage decrease, followed by a percentage increase of the same valulue will result in a change of value.Â
- Reducing a value by 20% is the same as retaining 80% of the value.Â
- Increasing a value by 20% is the same as 120% of the original value.
- Percent is a ratio.Â
- A rate can be helpful to determine percentage values.
Spark
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 60 seconds (or more) to do a rapid write on a piece of paper.
Then, ask students to share with their neighbours for another 60 seconds.
Finally, allow students to share with the entire group.
Some of the noticing and wondering that came up in a class recently included:
- I notice a bear is moving through two machines.Â
- How much does the bear cost?Â
- How big is the bear?Â
- Will the bear change size?Â
- How will the price change?Â
- Will the price even change?Â
- Why are we using a bear?
Sense Making
Crafting A Productive Struggle: Prompt
You may want to consider using this as a “numberless problem. You can share the following image with your students and have them discuss and choose their own price of the bear to explore how the price will change after the bear moves through both machines.Â
You can verbally share the following prompt with students:
What could be the final price of the bear after it passes through both price machines?
During Moves
While Students Are Productively Struggling…
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Student Approach #1: Benchmark Comparisons & Counting Up
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Student Approach #2: Indirect Comparison
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Student Approach #3: Using Equivalent Ratios
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Next Moves
Consolidation: Making Connections
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Reveal
Reflect
Provide students an opportunity to reflect on their learning by offering these consolidation prompts to be completed independently.
Consolidation Prompt #1:
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Consolidation Prompt #2:
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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.
Download Editable/Printable Handout
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Resources and Downloads
Lesson Tip Sheet
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Videos & Images
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Keynote Slides
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PowerPoint Slides
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Printable Handout
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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.
Consolidation Prompt #1
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Consolidation Prompt #2
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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