Problem solving ability of students do not develope optimaly. One of them is the unavailability of learning materials which facilitates students to increase students mathematical problem solving ability optimally. The purpose of this research is to produce learning instruments based on guided discovery that valid, practice, and effective to increase students mathematical problem solving ability on second semester at grade VIII of junior high school. Learning instruments that developed were lesson plan (RPP) and student worksheet (LKPD). This research is a development research with Plomp model that consists of three phases, namely preliminary research, development or prototyping phase, and assessment phase. Subjects were students of grade VIII of MTsS PGAI Padang. Data in this research were obtained from validation sheets for RPP, validation sheets for LKPD, sheets of observation for learning process, questionnaire for teacher, questionnaire for students, and final test. Data were analysed by descriptively. Based on the results, learning materials based on guided discovery can be concluded that the learning materials based on guided discovery to improve the student’s ability in mathematical problem solving on second semester at grade VIII of junior high school was valid, practice, and effective.
Keywords: Learning Material Based On Guided Discovery, Problem Solving Ability