The Development of a STEM-Based Student Worksheet on Flat-Surface Solid Geometry for Ninth-Grade Junior High School

This study aimed to develop a Science, Technology, Engineering, and Mathematics (STEM)-based Student Worksheet (LKPD) on three-dimensional shapes with flat surfaces for Grade IX junior high school students and to determine its validity, practicality, and effectiveness. The development was motivated by students' difficulties in understanding geometric concepts, identifying the elements of three-dimensional shapes, and accurately calculating surface area and volume. The study employed a Research and Development (R&D) approach, utilising the 4D model, which comprises the Define, Design, Develop, and Disseminate stages. The participants included two expert validators, one mathematics teacher, and 16 students from SMP Negeri 5 Banjarmasin. Data were collected through validation sheets, student response questionnaires, and evaluation tests, and were analysed quantitatively using a Likert scale and classical learning mastery percentage with a minimum mastery criterion of 75. The developed STEM-based LKPD encourages students to construct and test physical models of cubes and rectangular prisms, enabling them to explore relationships among mathematics, science, and engineering in real-world contexts. The results indicated that the LKPD achieved a validity score of 81.58% (valid), a practicality score of 86.91% (highly practical), and an effectiveness score of 81.25%, with most students meeting the minimum mastery criterion. These findings demonstrate that the STEM-based LKPD is valid, practical, and effective in promoting contextual and active mathematics learning.