Designed to provide intermediate grade students with experience using fractions and mixed numbers, the PLATO sequence described in this manual includes interactive models for students to work with, as well as lessons for review, practice, or experience. These lessons are intended to be integrated with the classroom mathematics instruction, and introductory materials describe the implementation of the lessons, student assignments, the student session, data feedback to teachers, and supplementary materials. The development of the curriculum and results of external evaluation studies are also briefly reviewed. The descriptions of 16 selected modules that make up the bulk of the manual include a statement of purpose, brief description, and sample computer displays for each lesson. Topics covered include the meanings, ordering and equivalence, conversions, addition, subtraction, and multiplication of fractions and mixed numbers, as well as the meanings of decimal fractions and conversions to or from fractions whose denominator is a power of 10. Appendices include samples of student responses in creative activities shared with other students, a brief review of some other uses of the PLATO fractions materials, simplified flow charts illustrating the instructional modules, a list of related publications, and an index to the lesson descriptions by title. (CHC)