Compressor at PT. Es Muda Perkasa that commonly failure is at unit D. So that need to optimize the compressor at unit D with finding the failure of the parts of the compressor and making the schedule of maintenance program to minimize the failure of the ice machine. This study using Reliability Centered Maintenance (RCM) method, which applicate Grey FMEA to determine the priority of the machine maintenance. After conducting and implementing the RCM method, it was found that the failure occurs at Low-Pressure and High-Pressure Pump at compressor unit D, and sub-part failure happen on bearing, due to small coefficient, which is 0.566 where it become primarily failure component. For the next maintenance, using schedule on condition task on bearing parts of the machine could minimize the failure of the parts on the machine

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The purpose of of this study is to determine the validity and practicality of a mathematics learning tools based discovery learning to facilitate the mathematical connection skills of students. This type of research is Research Development refer to 4D model.The development that the researchers carried out consisted of four stages, namely: (1) define; (2) design; (3) develop; (4) disseminate. The test subjects were 6 students of class X SMAN Plus, Riau Province. The research instrument used was a validity instrument in the form of a validation sheet to assess the feasibility of the syllabus, lesson plans and student worksheet. The validation of the learning tools by three experts. The results of the validation of the experts stated that the products that succeeded in reaching the very valid category with an average result for the syllabus were 9,98, RPP 3,95 and LKPD 3,77. In addition, this  mathematics learning tools meets the practical requirements in small group trials with an average student response questionnaire of 82,93% in the very practical category. Thus, the learning tools developed have met the valid and practical requirements to facilitate students' mathematical connection abilities

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