This is part two of a two-part SMSG mathematics text for junior high school students. Key ideas emphasized are structure of arithmetic from an algebraic viewpoint, the real number system as a progressing development, and metric and non-metric relations in geometry. Chapter topics include real numbers, similar triangles, variation, non-metric polyhedrons, volumes and surface areas, relative error, permutations and combinations, and probability. Slight revisions are contained in a later edition. (MP)