The first unit reviews and extends work with addition and subtraction as students review facts, look for patterns, and work with larger numbers. Unit 2 transitions to multiplication by having students use a variety of rich contexts (arrays of stamps, groups of windows, and a coral reef) to develop and refine multiplication strategies and models. Unit 3 returns to addition and subtraction, this time focusing on strategies for computing with larger numbers.

In Units 4 and 5, students explore measurement, fractions, division, and multiplication of larger numbers. They estimate and make measurements in different units; explore unit fractions and equivalent fractions, and begin adding and subtracting fractions; they connect multiplication to division and extend multiplication strategies to larger numbers. Their work with multiplication develops a strong understanding of area.

Unit 6 focuses on geometry, as students investigate, draw, and build two-dimensional shapes, using their properties to classify and analyze these shapes. They also connect geometry to fractions as they express the area of a shape as a unit fraction of the whole. Unit 7 brings together and extends many of the skills and concepts addressed in earlier units as students solve challenging problems that involve calculating with multi-digit numbers. They explore algorithms for addition and subtraction and dig deeper into division. Students develop strategies and models for division, many of which are based on their work with multiplication.

Unit 8 integrates mathematics and science, with a primary focus on designing and building model bridges. Students test the strength of their model bridges in systematic ways to collect data. Then they graph and analyze the data, finding the range and mean, to make conjectures and draw conclusions about effective bridge design and construction.