# Lesson 20

How Much in the Group? (optional)

### Lesson Purpose

The purpose of this lesson is for students to solve fraction division problems that ask: “How many in one group?”

### Lesson Narrative

In this optional lesson, students solve problems where a whole number quantity is a unit fraction of an unknown whole number.  In these situations students may rely on their understanding of the relationship between multiplication and division. For example, if 8 ounces is $$\frac{1}{4}$$ of the amount of water in a bottle, students might represent this with a tape diagram:

The tape diagram suggests the equation $$8 = \frac{1}{4} \times {?}$$ which students will likely solve by seeing that $${?} = 4 \times 8$$. The equation $$8 = \frac{1}{4} \times {?}$$ can also be written using division with the equation $${?} \div 4 = 8$$.

• Engagement
• MLR8

### Learning Goals

Teacher Facing

• Represent and solve problems involving division of a whole number by a unit fraction.

### Student Facing

• Let’s solve more problems involving multiplication and division with fractions.

### Lesson Timeline

 Warm-up 10 min Activity 1 20 min Activity 2 10 min Activity 3 10 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

What do you love most about math? How are you sharing that joy with your students and encouraging them to think about what they love about math?

### Suggested Centers

• How Close? (1–5), Stage 6: Multiply to 3,000 (Addressing)
• Rolling for Fractions (3–5), Stage 5: Divide Unit Fractions and Whole Numbers (Addressing)

### Print Formatted Materials

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