This textbook aims to develop all the mathematical power needed by the average person in the accurate control of his affairs. The purpose has been to teach first the most important topics of arithmetic and last those least frequently used. In consequence, the teacher may feel that the child who is leaving school at the end of any particular grade has been taught whatever would be most useful to him, considering that his schooling had to stop just then. Nothing in the next grade beyond is more important than what he has just studied. Books in this series are constructed to complete the fundamental processes of arithmetic by the end of the sixth year of school. No pupil studying from this course through the first six years will be left without an essential mathematical power. With this foundation, he can proceed by himself as needed to learn shorter or more convenient methods of calculation and to make new applications of the processes learned.