Learning Based Project as an Effective Strategy to Improve Student Understanding about Geometry Congested

Abstrak

Mathematics is often considered difficult because it requires deep conceptual and abstract understanding. Solid geometry is one of the most challenging topics for junior high school students. This study aims to determine the effectiveness of the Project Based Learning (PjBL) model in improving students' understanding of solid geometry. The study used Classroom Action Research (CAR) conducted in three cycles involving 21 seventh-grade students of SMP Melania II Jakarta during the 2024/2025 academic year. Data were collected through tests, observations, interviews, and documentation, and analyzed using descriptive quantitative methods. The results showed a continuous improvement in students' mathematical understanding across cycles. The average score increased from 46.33 in the pre-cycle to 59.72 in Cycle I, 82.50 in Cycle II, and 91.18 in Cycle III, while the percentage of students achieving the minimum mastery criteria (KKM = 75) increased from 14.29% to 87.25%. Students became more active, confident, and cooperative during the learning process. These findings indicate that Project Based Learning effectively enhances students' conceptual understanding and engagement in solid geometry.