Lesson 10
The Numbers in Subtraction
Lesson Purpose
Lesson Narrative
In earlier lessons, students explored addition and subtraction of fractions in context and out of context. They used diagrams to represent and find the values of sums and differences, and they also reasoned numerically. Students learned that a nonunit fraction can be decomposed—in at least one way—into a sum of other fractions with the same denominator. They recognized adding and subtracting fractions as joining and removing parts that refer to the same whole.
In this lesson, students apply these insights, as well as their knowledge of equivalent fractions from an earlier unit and from grade 3, to find differences of a whole number and a fraction.
 Representation
Activity 1: What’s Left?
Learning Goals
Teacher Facing
 Subtract a fraction from a whole number by decomposing the whole number and reasoning about equivalence.
Student Facing
 Let’s subtract fractions from whole numbers.
Required Materials
Materials to Copy
 Card Sort: Twelfths
Required Preparation
Activity 2:
 Create a set of cards for each group of 2.
CCSS Standards
Lesson Timeline
Warmup  10 min 
Activity 1  20 min 
Activity 2  15 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
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)
Print Formatted Materials
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Additional Resources
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