"Principles of Modern Elementary Mathematics (6 Grade)" is a sixth-grade level mathematics textbook, which examines and explores fundamental concepts of percentages, simple and compound interests, ratios and proportions, including polygons, polyhedrons, as well as circular and spherical bodies and other geometric concepts. It builds on the skills set attained in the 5th grade to extend the applications of basic arithmetic operations dealing with fraction, natural and fractional numbers. Theoretical treatment is synergized with practical considerations in the form of featured examples, exercises, problems with solutions and explanations to ensure that even the dullest pupil can acquire the deepest understanding, knowledge and the required skills set. The text is designed to promote and enhance the teaching and learning experiences for both teachers and pupils. "Principles of Modern Elementary Mathematics (6 Grade)" is intended and recommended not only for 6th grade pupils and their teachers, but also for an adult literacy program in which basic mathematics concepts and skills are taught. It is a contribution to the development and improvement of a community school curriculum on elementary mathematics.