Commercial arithmetic is a fundamental component of the mathematics curriculum, providing
students with essential skills for real-life financial tasks such as budgeting, interest computation,
and general money management. This study explores the factors affecting the teaching and
learning of commercial arithmetic in public secondary schools within Kibera Sub-County,
Nairobi County. Specifically, it investigates the influence of teaching and learning resources,
teacher qualifications, student motivation, and socio-economic conditions on instructional
effectiveness and learner outcomes. The study adopts a mixed-methods approach, integrating
both quantitative and qualitative data collection techniques. Data were obtained from
mathematics teachers, students, school administrators, and parents through questionnaires,
interviews, focus group discussions, and classroom observations. Quantitative data were
analyzed using descriptive and inferential statistics, while qualitative data were subjected to
thematic analysis. Findings from the study revealed critical insights into the challenges and
enabling factors surrounding commercial arithmetic instruction in resource-constrained school
environments. The study offers practical recommendations for enhancing the quality of teaching
and learning in mathematics and contributes to evidence-based policymaking aimed at improving
educational outcomes in Kibera Sub-County.