Lesson plan

# 6. Solve problems with related facts (A)

teaches Common Core State Standards CCSS.Math.Content.1.OA.C.6 http://corestandards.org/Math/Content/1/OA/C/6
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP2 http://corestandards.org/Math/Practice/MP2

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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)

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)
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• 6. Solve problems with related facts (A)