Design and Development of a Project-Based Learning Mathematics Teaching Module for Geometry in Second Grade of Elementary School Based on Expert Consensus

Project-based learning in mathematics education has demonstrated potential for enhancing student engagement and conceptual understanding.However, systematic validation of project-based learning instructional modules for elementary geometry remains limited, particularly within contemporary curriculum frameworks.This study addresses this gap by designing, developing, and validating a comprehensive project-based learning mathematics teaching module for elementary geometry instruction aligned with Indonesia's Merdeka Curriculum.Using design and development research methodology, the study integrates the Fuzzy Delphi method and Content Validity Index analysis for module validation.Fifteen subject matter experts participated in Fuzzy Delphi rounds to establish consensus on module components, while three mathematics education experts conducted content validation analysis.Results demonstrate robust expert consensus on problem-oriented learning scenarios, collaborative activities, and project-based assessment mechanisms.Content validation yielded high validity indices for most module components, with minor refinements recommended for specific elements.The study contributes methodologically by combining expert consensus with quantitative validation techniques, theoretically by providing an evidence-based framework for mathematics module development, and practically by delivering a validated geometry module for classroom implementation.Future research should evaluate the module's effectiveness through classroom implementation studies and explore adaptation for other mathematical domains.