Lesson Objective: Understand that the meaning of addition and subtraction extend to fractions.

This lesson helps build conceptual understanding that the operations of addition and subtraction can be used with fractions. The meaning and uses of the operations does not change when we incorporate a new type of number. The concept is developed through the use of bar models to show known and unknown values in a word problem. Student write addition and subtraction equations to model situations given with whole numbers, and then model and write equations for problems using fractions. Finding sums and differences is not expected in this lesson, but students may reason about the unknown values using their understanding of fractions. Students bring prior knowledge of addition and subtraction from earlier grades, including the relationship between the two operations. This knowledge helps students as they model situations and write related equations with unknown values. Students engage in Mathematical Practice 4 (Modeling with mathematics) as they model situations with bar models and equations. This supports students as they incorporate fractions into their understanding of the meaning and uses of addition and subtraction. Mathematical Practice 7 (Look for and make use of structure) is also featured in this lesson as students connect the structure of addition and subtraction equations across different types of numbers.

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