## BARNYARD [DAY 5]

### Subtraction: Counting Back and Adding Up

Investigate early subtraction strategies through counting back and adding up to find the difference.

## Intentionality & Unit Overview

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Students will continue exploring subtraction and using a strategy that is flexible based on the numbers presented in the question. The visual math talk and purposeful practice that could be used in small groups and for an assessment opportunity.

The purpose of the Day 4 activities is to reinforce key concepts from Day 3. Students will engage in 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.

• Subtraction names the missing part in terms of the whole
• Counting back is efficient when the count back is small
• Adding up to find the difference is efficient with the subtrahend is close in value to the minuend
• Addition and subtraction are related in that addition names the parts in the whole and subtraction uses the whole to find a missing part.
• Subtraction can be used in either take away, comparison, or missing addend situations.

Assessment

This checklist can be used for tracking formative assessment as students are working. The information collected can be used to form whole group, small group or one-to-one support models.

## Math Talk

In today’s math talk, students will be exposed to a number sentence to represent subtraction questions. Students may need a reminder at the beginning of the meaning behind the symbol because it may seem very abstract to students.

Similar to Day 4, the purpose of today’s math talk is to expose students to questions when it would be most efficient to use the strategy of “counting back” and questions when it be most efficient to use the strategy of “adding up”. The string will start with counting back which is the strategy that students are typically more comfortable with followed by questions with purposefully chosen numbers that would be much easier if added up instead. This will present the opportunity for a discussion about why the numbers in a question will help decipher the proper strategy to choose.

## Visual Math Talk Prompt #1

This Number Talk is presented in a string to show students both strategies back to back.

With 9 – 1, it is more efficient to count back 1 because the count is small versus 9 – 8, it is more efficient to add up from 8 because 8 and 9 are close together.

The number line is used as a tool to demonstrate the count back. Highlight the space between 9 and 8, to show that the count back is small. Also, point out that only 1 has been subtracted as shown in the semi-circle jump.

This number line looks very similar to the first part of the string, but it is showing that we are adding up because the numbers are so close together.

## Visual Math Talk Prompt #2

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## Visual Math Talk Prompt #3

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## Assessment Considerations…

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## Assessment Opportunity: Game

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## Assessment Opportunity: 1:1 or Small Group

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## Assessment Opportunity: Independent

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## Considerations to Promote Student Growth

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