Prior to 3rd grade, fraction concepts are addressed in other domains--mainly geometry-- as students learn that a whole figure can be "shared fairly" by dividing it into equally sized pieces. In 3rd, 4th, and 5th grade, Numbers and Operations--Fractions is designated as its own domain. The Fractions domain of the CA Common Core Content Standards is about becoming familiar with the number system of fractions, by learning skills such as: modeling fractions with various types of models, comparing, ordering, converting between improper fractions and mixed numbers, adding, subtracting, finding common denominators, and learning how decimals work. All of these foundational fraction concepts prepare students for middle school and beyond, where they will work with the full extent of rational numbers within all problem types.