# Lesson 11

Subtract Fractions Flexibly

### Lesson Purpose

The purpose of this lesson is for students to subtract fractions, including mixed numbers, by decomposing numbers and writing equivalent fractions, and to recognize when these strategies are useful for finding differences.

### Lesson Narrative

In the previous lesson, students learned to subtract a fraction from a whole number numerically, by writing an equivalent fraction for the whole number or decomposing the whole number into a sum of fractions with the name denominator. This lesson extends that work to include mixed numbers. It also prompts students to look for structure in subtraction expressions where decomposing one or both numbers makes the expression easier to evaluate (MP7). The work here builds students’ ability to subtract fractions flexibly.

- Action and Expression

### Learning Goals

Teacher Facing

- Subtract fractions and mixed numbers by decomposing numbers and reasoning about equivalence.

### Student Facing

- Let’s find all kinds of differences.

### Required Materials

Materials to Gather

### Required Preparation

- Each group of 4 needs tools for creating a visual display during the lesson synthesis.

### 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

Reflect on evidence of student thinking that you observed today. Whose thinking was voiced and heard? Whose thinking was not but could have enriched the conversations? What prompts or structures might better enable the latter to share their voice and reasoning?

### Suggested Centers

- Compare (1–5), Stage 6: Add and Subtract Fractions (Addressing)
- Rolling for Fractions (3–5), Stage 2: Multiply a Fraction by a Whole Number (Addressing)
- Creating Line Plots (2–5), Stage 2: Quarter Inches (Supporting)