Standard

Explain why addition and subtraction strategies work, using place value and the properties of operations.

Student language:

• "I can explain why I need to use addition or subtraction to help me solve problems."

Explanation

About the Math, Learning Targets, and Rigor

This standard calls for the student to explain using concrete objects, pictures and words (oral or written) why addition or subtraction strategies work. The expectation is that students apply their knowledge of place value and the properties of operations in their explanation.

Understanding place value and then being able to describe how it works when computing, along with the properties of operations, is expected. Students don’t need to name the properties but they need to know that they can use them and how to use them when computing. Also include incorrect examples for students to examine.

Representations can include numbers, words (including mathematical language), pictures, number lines, and/or physical objects. Students should be able to use any/all of these representations as needed.

Resources

Videos

• Khan Academy
  • scroll to find 2.NBT.9, click on a skill, watch videos on left side in each skill
• Learn Zillion

EngageNY Lessons

Extra Practice

• North Carolina Tasks
• Illustrative Math Tasks
• Howard County Tasks
  • Click on 2nd grade at bottom, then 2.NBT.9
• Common Core Sheets

Released Assessment Questions

2.NBT.9 Student Example

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