Unit 4 focuses on the foundational fraction concepts. Students will build on the Grade 2 expectation of partition circles and rectangles into two, three, or four equal shares, and describe the shares using the words halves, thirds, or fourths. Students also build on their work with area in the previous unit to partition shapes into parts with equal areas. They come to understand unit fractions as quantities formed by partitioning a whole into equal parts. Students will use visual fraction models to represent simple fractions, to generate simple equivalent fractions, and to compare two fractions by reasoning about their size. Students will also understand fractions as numbers by placing them on the number line, and that all fractions are built from unit fractions.