PLENTIFUL POMEGRANATES [DAY 2]
SUBTRACTION STRATEGY: PLACE VALUE TO ALGORITHM
Explore efficient strategies to subtract values within 50
Intentionality
Math Talk
Visual Math Talk Prompt #1
Visual Math Talk Prompt #2
Visual Math Talk Prompt #3
Visual Math Talk Prompt #4
Purposeful Practice
Resources & Downloads
Educator Discussion Area
Intentionality & Unit Overview
Length of Unit: 5 Days
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Students will be presented with a subtraction context and explore the place value as a strategy to solve the problem.
Intentionality…
The purpose of the Day 2 activities is to reinforce key concepts from Day 1. Students will engage in a string of related problems through a math talk and will have an opportunity to complete purposeful practice. The math talk and purposeful practice serve to develop a deeper understanding of the following big ideas.
Some of the big ideas that may emerge today include:
- Understanding hierarchical inclusion allows for flexible composing and decomposing of numbers
- Numbers can be decomposed by separating a whole into two or more parts
- 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 take away, comparison, or missing addend situations. This task will explore the take away method.
- Models can be used to connect concrete to abstract
Math Talk
To practice using a place value strategy, have your students work through these problems one at a time. As you present each problem, provide students with some quiet, individual think time during which they can solve the problem and show their thinking on a dry erase board, paper, etc. Then have students share their thinking either in pairs or with the whole group. As you facilitate these conversations, it will be important to highlight how numbers can be decomposed to use place value when subtracting.
The number prompts are created to lead students through the process of using place value as a strategy for subtraction. The first string and prompts do not require regrouping. The last prompt could be used as a diagnostic for Day 3. What are students doing when regrouping/exchanging from a higher place value is necessary?
String 1:
20 – 10
30 – 20
40 – 10
Prompt 2:
25 – 12
Prompt 3:
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Prompt 4:
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Visual Math Talk Prompt #1
Visual Math Talk Prompt #2
This prompt uses numbers that still do not require regrouping/exchanging from the higher place value column. The base ten blocks are on a place value chart to help generate a discussion about only removing one place value at a time. Students can remove 1 from the tens place value and 2 from the ones/singles column.
Visual Math Talk Prompt #3
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Visual Math Talk Prompt #4
Purposeful Practice
Small Group Game
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Small Group Assessment Opportunity
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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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