# 4. Comparing strategies to add mixed numbers (A)

teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3c http://corestandards.org/Math/Content/4/NF/B/3/c
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3

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Lesson objective: Compare strategies for adding mixed numbers.

This lesson provides an opportunity for students to apply their knowledge and understanding of adding mixed numbers to a mathematical situation. Students are asked to compare two strategies for adding mixed numbers and justify which method they believe works better.

Key Concept students will use:

• Replacing a mixed number with an equivalent fraction and using the relationship between addition and subtraction can make it easier to add and subtract fractions with like denominators.

Skills students will use:

• decomposing fractions; (Grade 3, Unit 4)
• making whole numbers into equivalent fractions; (Grade 3, Unit 10)
• decomposing mixed numbers

Students engage in Mathematical Practice 3 (Construct viable arguments and critique the reasoning of others) as they create examples and justify their choice of strategy for adding mixed numbers.

Key vocabulary:

• fraction
• mixed number

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