This study investigates the effectiveness of Guided Inquiry-Based Instruction (GIBI) integrated with Variation Theory in improving grade ten students’ solid geometry achievement in Debre Tabor City, Ethiopia. A quasi-experimental design involving 99 students found in three classes from three government schools assigned them randomly to three groups: Experimental Group 1 (EG1, n=30) received GIBI with Variation Theory, Experimental Group 2 (EG2, n=37) received only GIBI and the Control Group (CG, n=32) followed traditional methods. Pre- and post-tests analyzed using ANCOVA and paired t-tests revealed significant improvements, with EG1 achieving the highest scores (p = .000). Effect sizes were substantial for EG1 (Cohen's d = 1.50) and EG2 (d = 1.39) compared to CG (d = .73). The results highlight that GIBI combined with Variation Theory significantly enhances students’ solid geometry achievement, emphasizing the value of such kind of innovative teaching strategy to foster students’ achievement in similar educational contexts. 

Understanding and handling diversity, as well as inclusion, are critical in ensuring effective teaching and learning, especially in the mathematics classroom, where students have varied abilities. Despite the growing research in inclusive education, little is known about how mathematics teachers in the Ghanaian context understand the theory of multiple intelligences (MIs), leaving a gap in how this theory can be applied in the classroom to improve practice and inclusion. In this study, the authors explored Ghanaian mathematics teachers’ conceptions of the theory of MIs using a basic qualitative method design. 12 senior high school mathematics teachers in one municipality of Ghana were engaged through questionnaires and semi-structured interviews, including field notes, to provide information on their conceptions of the theory of MIs. Thematic analysis revealed that mathematics teachers conceived the theory of MIs as a theory of different styles for learning, multiple teaching strategies, and a theory for catering to diverse student needs. The findings highlight the need for professional development and teacher training curriculum development to enhance teachers' understanding of the theory of MIs to improve their practice and handling of inclusiveness and diversity in the classroom.