Providing a basic understanding of arithmetic and problem-solving techniques for water and wastewater operators, this book introduces and reviews fundamental concepts critical to qualified operators. Presented at a basic level, this volume reviews fractions and decimals, rounding numbers, significant digits, raising numbers to powers, averages, proportions, conversion factors, flow and detention time, and the areas and volumes of different shapes. It builds a strong foundation based on theoretical math concepts, which it then applies to solving practical problems for both water and wastewater operations.