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# 3. Adding mixed numbers using the associative and commutative properties (FP)

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.MP2 http://corestandards.org/Math/Practice/MP2

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Lesson objective: Practice adding mixed numbers by decomposing the mixed number into a whole number and fraction and then applying the communicative and associative properties.

This lesson helps to build procedural skill with adding mixed numbers. Deliberate use of vocabulary is used here because it supports the connection between a mixed number as a single number and as a sum of a whole number and a fraction. This work develops students' understanding that replacing a mixed number with an equivalent sum and using the relationship between addition and subtraction can make it easier to add and subtract fractions with like denominators.

Students engage in Mathematical Practice 2 (Reason abstractly and quantitatively) as they consider how to write equivalent forms of mixed numbers. Students will also practice using properties of math to add the whole number parts and fractional parts of the mixed numbers separately and then put them together again as a mixed number.

Key vocabulary:

• fraction
• mixed number
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