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Lesson Plan

6. Solve problems with related facts (A)

teaches Common Core State Standards 1.3D
teaches Common Core State Standards 2.4A
teaches Common Core State Standards 1.CA.1
teaches Common Core State Standards CCSS.Math.Practice.MP2
teaches Common Core State Standards CCSS.Math.Content.1.OA.C.6
teaches Common Core State Standards CCSS.Math.Practice.MP1
teaches Common Core State Standards MAFS.1.OA.3.6
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Lesson objective: Solve addition and subtraction problems where both "parts" are unknown.

This lesson provides an opportunity for students to apply their knowledge and understanding of addition and subtraction to a real-life situation. Students are asked to figure out how many goldfish and clownfish are in a tank when there are 19 fish in all. 

Key Concept students will use: 

  • We can use strategies such as making ten, counting on, decomposing a number leading to a ten, and the relationship between addition and subtraction to add and subtract within 20.

Skills students will use:

  • Understand addition and subtraction are related
  • Apply properties of operations as strategies to add and subtract (Grade 1, Unit 6)
  • Understand subtraction as an unknown-addend problem (Grade 1, Unit 6)

Students engage in Mathematical Practice 4 (reason abstractly and quantitatively) as they solve problems with both parts unknown.

Key vocabulary: 

  • equal
  • part
  • total
  • whole

Special materials needed:

  • Part Part Total Worksheet (optional)
  • counters or cubes (optional)
Related content

Appears in

Extending strategies for solving addition and subtraction problems

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