In sixth grade, students learn key concepts along the progression toward middle school algebra. Ratios and proportions emerges as a new domain of study, where students explore and reason with ratios and rates in order to solve problems. Sixth graders will also investigate negative numbers for the first time and round out their study of the rational number system before operating with all rational numbers in seventh grade. Work with numerical expressions extends to algebraic expressions, which sets students up to solve one-step equations and inequalities. Students will also continue their study of area and volume of geometric shapes, and will learn how statistics can be used to better understand data about our world.