Subtracting Fractions Justifications

Introduction

• Write four subtraction expressions on the board where one expression has like denominators and the other expressions have unlike denominators (e.g., ²⁄₇ − ⅚, ⁹⁄₁₂ − ⁵⁄₁₂, ⁶⁄₁₀ − ⁴⁄₁₀, and ⅕ − ⁹⁄₁₁) . Ask students to think about which one of the four expressions does not belong. Allow them to think on their own for 30 seconds before sharing their thoughts with their partners.
• Have some partnerships share their ideas aloud and write some of the ideas on the board that focus on key vocabulary terms (i.e., "denominator," "unlike," "subtraction," "common denominator," etc.).
• Have a volunteer read the student-friendly language objective that is written on the board: "I can describe how to subtract fractions with unlike denominators using repeated explanations and peer input." Define the key terms, such as "describe," "unlike," "denominators," "explanations," and "peer conversations."
• Ask students for examples of each of the vocabulary terms and write them around the terms in the language objective.