Determining Unknown Numbers

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Not all the numbers are always there and in this lesson that is just what the students will learn. Students will learn to determine an unknown number in an addition or subtraction equation. Find the number and you will find the answer.

Determining Unknown Numbers Lesson Plan Includes:

  • Full Teacher Guidelines with Creative Teaching Ideas
  • Instructional Content Pages about Determining Unknown Numbers
  • Hands-on homework activities giving students practice on comparing and contrasting Determining Unknown Numbers
  • Answer Keys
  • Common Core State Standards
  • Many Additional Links and Resources
  • Built for Grades 1-3 but can be adapted for other grade levels.

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Description

Not all the numbers are always there and in this lesson that is just what the students will learn. Students will learn to determine an unknown number in an addition or subtraction equation. Find the number and you will find the answer.

  1. Begin by explaining to students that different parts of addition or subtraction sentences may be missing and they will have to find that missing part.
  2. While reading the content pages, reinforce vocabulary and give students additional examples of determining unknown number problems in order to help them practice the new skill. Use the additional resources to enhance understanding.
  3. Introduce the notes on determining unknown numbers. Have students practice problems with addition and subtraction.  Use the additional resources to enhance understanding.
  4. Have students practice problems using fact families in order to help them solve for the missing part or whole.
  5. Follow the Activity page with students. Start with a specific number of cotton balls and have the students count them.  Have students close their eyes and then hide some under a cup.  Have students count how many cotton balls are remaining and then find the missing addend.  Have students fill in their chart.
  6. Distribute Practice page. Check and review the students’ responses as you walk around the class.
  7. Distribute the Homework page. Have students work a few problems at the beginning of the next class to reinforce the new skill.
  8. In closing, ask students how they thought through finding a missing part to the whole.
  9. Allow for responses and discussion.

Common Core State Standards: 

CCSS.Math.Content.1.OA.D.8

CCSS.Math.Content.2.OA.A.1

None for Grade 3

Class Sessions (45 minutes): 1 class

Additional Resources:

Want more math resources? Check out our other Math Lesson Plans!

Additional information

Grade Level

4th Grade, 5th Grade

Subject

Science