I know the topic of common denominators has been discussed extensively on the “Drafty Drafts” page but I need some clarification regarding 4.NF.2. The standard asks students to compare fractions with different numerators or denominators. With different denominators, the example is given of finding a common denominator to aid comparison.
The NF Progressions doc (page 5) seems to suggest that students rely on a “numerical process” for finding common denominators once they understand equivalence using pictorial models (as shown in the margin of page 5). Is it expected that most students by the end of Grade 4 will create common denominators “numerically” by multiplying the denominators together?