Standard

Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.

Student Language:

• "I can use what I know about addition facts to help me answer subtraction fact problems."

Explanation

About the Math, Learning Targets, and Rigor

This standard asks for students to use subtraction in the context of unknown addend problems. When determining the answer to a subtraction problem, 12 − 5, students think, “If I have 5, how many more do I need to make 12?” Encouraging students to record this symbolically, 5+? = 12, will develop their understanding of the relationship between addition and subtraction.

Some strategies they may use are counting objects, creating drawings, counting up, using number path or 10 frames to determine an answer.

Resources

Videos

• Khan Academy
  • Scroll to 1.OA.4, click on skill, find videos on left side of each skill

Extra Practice

• North Carolina Tasks
• Illustrative Math Tasks
• Howard County Tasks
  • Click on 1st grade at bottom, then 1.OA.4
• Common Core Sheets