<![CDATA[Problem solving is an essential competency in 21st-century mathematics education. However, implementing Problem-Based Learning (PBL) still faces challenges in using authentic problems and has rarely integrated Computational Thinking (CT) and 21st-century interdisciplinary themes systematically. This study aimed to develop a PBL-based student worksheet that integrates CT and 21st-century interdisciplinary themes to support students' real-life problem-solving. The study employed the ADDIE model, consisting of the analysis, design, development, implementation, and evaluation stages. The developed worksheet was validated by experts, evaluated for practicality through teacher and student responses as well as learning implementation, and tested for effectiveness using a posttest-only control group design. The results showed that the worksheet has three main characteristics: integrating CT into every phase of PBL, using 21st-century interdisciplinary themes as authentic problem contexts, and including learning activities that systematically guide students through the real-life problem-solving process. The evaluation results indicated that the worksheet was valid, practical, and effective. Its effectiveness was demonstrated by students' real-life problem-solving performance, which was significantly better than that of students receiving standard PBL instruction, and by the achievement of classical learning mastery, with at least 80% of students meeting the predetermined mastery criterion. Keywords: 21st century interdisciplinary themes, computational thinking, problem-based learning, problem solving.]]>
