Lesson 3

The purpose of this lesson is for students to use the meaning of numerator and denominator and to compare fractions with the same numerator or the same denominator.

In this lesson, students reason about the relative size of fractions based on the meaning of numerator and denominator, and use fraction strips to support their reasoning. 

Students first compare pairs of fractions with the same denominator. They recall that fractions with the same denominator are composed of the same unit fractions or have parts that are the same size, so the numerators can tell us how the fractions compare: the greater the numerator, the greater the fraction. 

Next, students compare fractions with the same numerator. They recognize that we cannot simply look at the denominators and see which is greater. Because the denominator tells us the number of parts in 1 whole, the greater that number, the smaller the fractional part. 

Most students may find it more intuitive to compare fractions with a common denominator than those with a common numerator. Did you see students who grasp both equally well? How did they conceptualize the latter?