The document evaluates Navy Group Four personnel gains in basic arithmetic skills after taking experimental courses in linear measurement and recipe conversion. Categorized as Mental Group Four by receiving scores from the 10th to the 30th percentile of the Armed Forces Qualification Test, trainees received instruction tailored to the level of their abilities and presented within a vocational context. Instruction in measuring linear dimensions was given to 26 Group Four trainees and recipe conversion was taught to 17 Group Four trainees and 23 Commissaryman personnel. All trainees worked individually and at their own rate, with test results showing Group Four personnel achieving proficiency in only some of the required skills. Concluding that mathematical learning capacities of Group Four personnel did not appear to be adequate for learning to perform typically required computational tasks of Navy enlisted men, despite experimental changes in coursework presentation, it is stated that the nature of the difficulties experienced by this group must be clarified before further improvement in training can be accomplished. Tabulation of test results is included and descriptions of meld test problems, the recipe conversion test, and the diagnostic mathematics quiz are appended. (LH)