One of the major challenges in mathematics education is improving students’ performance and interest simultaneously. Instruction that emphasizes the use of multiple solutions in modeling problems can contribute to the construction of mathematical knowledge; however, their motivational benefits are not yet fully understood. The present study aimed to examine the effect of an instructional intervention designed to enhance students’ interest and mathematical performance.



The study employed an explanatory mixed‑methods design, including a quasi‑experimental quantitative phase and a qualitative case study. The instruments for measuring performance consisted of seven researcher‑developed tests, and students’ interest was assessed through a questionnaire and interviews. Participants included 76 students in the experimental group and 93 ninth‑grade female students in the control group from two public schools in District 3 of Tehran. The instructional intervention was implemented in seven sessions and focused on developing multiple solutions for open‑response mathematical modeling problems through small‑group work.



Students’ performance was assessed using modeling tests whose validity was confirmed through expert judgment and whose reliability was established using Cronbach’s alpha. Students’ interest was measured using a Likert‑scale questionnaire based on the framework proposed by Luding and Zhu (2008), and the data were analyzed using the Friedman test. The results indicated a significant increase in both students’ interest and mathematical performance in the experimental group