Gr 4-8-These titles effectively combine science or social studies with mathematics. Each book poses realistic mathematical problems and solutions that relate to it. Mesopotamia describes how civilization began between the Tigris and Euphrates rivers, and how the abundant resources and fertile soil enabled previously nomadic people to settle, become farmers, and establish a government. Mathematical problems include multiplication, division, percentages, and determining area and volume. Sumerian and Babylonian number systems, including cuneiforms and the base 10 number systems, are compared. Electoral College explains why the process was formed and how it works. Pie, bar, and scatter graphs are used to compare the popular and electoral votes in various elections, including that of 2000. Barrier Reef explains how these reefs are formed and their importance to the ecosystem. Charts show the numbers of species found in them, and the calculation of percentages is taught. Line, bar, and pie graphs compare coral production, the percentages of coral on inshore and barrier reefs, and the number of visitors to the area. Transcontinental Railroad describes the political, economic, and social conditions that affected the building of this transportation system. Mathematical problems using ratios, proportions, and algebraic equations are used to determine the cost for laying each mile of track, the profit made by selling stock in the railroad companies, and the number of rails laid in a certain time period. All of these titles would be appropriate additions. -Ann Joslin, Fort LeBoef School District, Waterford, PA Copyright 2007 Reed Business Information.