Book excerpt: Ratios and Proportions Workbook covers the concept of the ratio of two quantities. From this concept, we develop the related concepts of a rate (so much of one thing per so much of another thing) and a proportion (an equation of ratios). We also study how tables of equivalent ratios can help to solve problems with rates, and how cross-multiplying can help to solve problems with proportions. The lesson Unit Rates defines the concept of the unit rate, shows how to calculate one, and gives practice at doing so, including practice with complex fractions. We also consider rates as two quantities that vary, graph the corresponding equation in the coordinate grid, and tie in the concept of unit rate with the concept of slope. The concept of direct variation is introduced in the lesson Proportional Relationships. Writing and graphing equations gives a visual understanding of proportionality. In two following lessons on proportions, students also practice solving rate problems in different ways, using the various methods they have learned throughout the workbook. The lessons Scaling Figures, Floor Plans, and Maps give useful applications and more practice to master the concepts of proportions. Before the Review there is also an optional lesson, Significant Digits, that deals with the concept of the accuracy of a measurement and how it limits the accuracy of the solution. It is optional because significant digits is not a standard topic for seventh grade, yet the concept in it is quite important, especially in science.