Lesson objective: Solve mixed number addition and subtraction problems by using the relationship between addition and subtraction.

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 find missing sums, addends, differences and subtrahends.

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 2 (Reason abstractly and quantitatively) as they add and subtract mixed numbers by writing equivalent forms of mixed numbers, either as fractions or sums of whole numbers and fractions and think flexibly to solve challenging problems.

**Key vocabulary: **