<![CDATA[Geometry is a branch of mathematics crucial in developing students' thinking skills. International and national studies show that students have a low understanding of geometry concepts, especially the volume of space. It is caused by learning that does not facilitate building students' understanding. This study aims to develop and implement a Hypothetical Learning Trajectory based on Inquiry Learning (HLT-IL) to facilitate elementary students' understanding of the volume of cubes and blocks. A design research methodology comprised three main phases: preparing for the experiment, conducting the teaching experiment, and retrospective analysis. The study's instruments consisted of worksheets, observation sheets, and tests. The participants were fifth-grade students categorized into three skill levels: low, medium, and high. The resulting HLT-IL comprised five main activities: orientation, conceptualization, investigation, conclusion, and discussion, and nine sub-activities: introduction and discovery, questioning, hypothesis generation, exploration, experimentation, data interpretation, summarizing and comparing, communication, and reflection. The results showed that 26 out of 28 students (92.86%) reached the satisfactory category, while 2 students (7.14%) remained in the unsatisfactory category. These findings indicate that the inquiry-based learning trajectory can be an effective alternative for supporting conceptual discovery, particularly in learning the volume of space in primary education.]]>
