Lesson 15 Common Denominators to Compare

    • Let’s compare fractions by writing equivalent fractions with the same denominator.

Warm-up What Do You Know About …?

What do you know about 15 and 30?

Activity 1 Tricky Fractions?

Problem 1

In each pair of fractions, which fraction is greater? Explain or show your reasoning.

  1. or

  2. or

Problem 2

Han says he can compare and by writing an equivalent fraction for . He says he can’t use that strategy to compare and . Do you agree? Explain your reasoning.

Problem 3

Priya and Lin showed different ways for comparing and . Make sense of what they did. How are their strategies alike? How are they different?

Priya: 

​​ is greater than , so ​​​​​ is greater than .

Lin: 

is greater than , so is greater than .

Activity 2 Use a Common Denominator, or Not

Problem 1

For each pair of fractions, write a pair of equivalent fractions with a common denominator.

  1. and

  2. and

  3. and

  4. and

Problem 2

For each pair of fractions, decide which fraction is greater. Be prepared to explain your reasoning.

  1. or 

  2. or 

  3. or 

  4. or 

Practice Problem

Problem 1

  1. List these fractions from least to greatest.

  2. Explain or show your reasoning.