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Mathematics is a science that plays a very important role. Mathematics sharpens many abilities, one of which is problem solving ability. However, students' mathematical problem solving abilities are still low, so it is necessary to develop learning tools that can improve students' mathematical problem solving abilities. The development of learning tools needs to be developed to support the quality of education. The aim of this research is to develop discovery learning model learning tools to improve students' mathematical problem solving abilities. This research uses the Plomp model with the aim of producing valid, practical and effective criteria.

mathematics, education, problem solving, discovery learning, valid, practical, effective.