MATHCO is a motivating series of audiovisual and print materials designed to overcome the negative effects of sex bias and stereotyping on the attitudes, interests, and aspirations of girls toward mathematics and mathematics-related careers. The materials teach mathematics skills, demonstrate relationships between mathematics and other subjects, and provide exposure to mathematics-related careers. They are useful for boys as well as girls at the pre- and early-adolescent stage; they are both multiethnic and nonsexist in text and illustrations. Module 4 focuses on practical applications of mathematics, including making change, adjusting recipes, unit pricing, ordering from catalogs, building a doghouse, and calling long distance. Activities and activity worksheets are included, in addition to the audiovisual script. (MNS)