<![CDATA[Mathematical problem-solving ability is a crucial competency in elementary school mathematics education. However, low levels of learning activity and a lack of instructional variety remain challenges in developing this ability, particularly regarding the topic of 2-dimensional (2D) shapes. This study aimed to analyze changes in students' mathematical problem-solving abilities following instruction using the Contextual Teaching and Learning (CTL) approach assisted by geoboards, and to examine the relationship between learning activity and mathematical problem-solving scores. A quantitative approach was employed using a pre-experimental one-group pretest-posttest design. The study subjects consisted of 40 fourth-grade students from primary school (SD) 5 Ngabul. Data were collected using a mathematical problem-solving test based on Polya’s stages and an observation sheet for student learning activity. Data analysis was conducted using the Paired Sample T-test and simple linear regression. The results showed an increase in the average mathematical problem-solving score from 41.85 to 70.13 following the instruction. Furthermore, student learning activity showed a positive relationship with posttest scores, with a coefficient of determination of 56.1% for the study sample. The findings indicate that CTL instruction assisted by geoboards serves as a viable alternative teaching method to foster student engagement and the development of mathematical problem-solving skills.]]>
