Lesson 8

Add and Subtract Fractions

Lesson Purpose

The purpose of this lesson is for students to add fractions with unlike denominators in a way that makes sense to them.

Lesson Narrative

In this lesson, students add and subtract fractions in a way that makes sense to them. They consider several important cases:

  • The denominators of the two fractions are the same, which is review of work from a previous grade.
  • One denominator is a multiple of the other so the fractions can be added by replacing only one of the fractions with an equivalent fraction.
  • Neither denominator is a multiple of the other so a third new common denominator is needed to add the fractions.
Students describe how the situations are different and find the sums and differences in a way that makes sense to them. The denominators of the fractions used in this lesson are familiar from grade 3, inviting students to use a variety of different familiar representations.
  • Action and Expression
  • MLR8

Activity 2: Add and Subtract

Learning Goals

Teacher Facing

  • Add and subtract fractions with unlike denominators in a way that makes sense to them.

Student Facing

  • Let’s add and subtract fractions.

Required Materials

Materials to Copy

  • Fraction Add and Subtract Sort

Required Preparation

Activity 1:

  • Create a set of cards from the blackline master for each group of 2.

CCSS Standards

Addressing

Lesson Timeline

Warm-up 10 min
Activity 1 15 min
Activity 2 20 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

Which students had opportunities to share their diagrams and thinking during whole-class discussion? How did you select these students?

Suggested Centers

  • Would You Rather? (2–5), Stage 3: Compare Units in a Given System (Addressing)
  • Compare (1–5), Stage 6: Add and Subtract Fractions (Supporting)

Print Formatted Materials

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Additional Resources

Google Slides

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PowerPoint Slides

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