Abstract

Numeracy literacy constitutes a fundamental component of functional literacy and is essential for independent functioning, adaptive behavior, and participation in everyday life. However, children and adolescents with intellectual and developmental disabilities often experience substantial difficulties in acquiring foundational arithmetic skills due to challenges in numerical reasoning, working memory, abstraction, and problem solving. The present study aimed to systematically synthesize empirical and review evidence on instructional approaches designed to support the development of functional numeracy literacy through arithmetic interventions among these learners. The review was conducted in accordance with the PRISMA 2020 framework. Relevant literature was identified through systematic searches of Scopus, Web of Science, ERIC, and Google Scholar using predefined search terms and eligibility criteria. Following screening and full-text assessment, 36 studies were included in the qualitative synthesis. Of the 36 included studies, 22 were empirical intervention studies, 6 were systematic reviews or evidence-based practice reviews, 2 were meta-analyses, 1 was a correlational study, and 5 employed other research designs, including content analyses, intervention syntheses, and classroom-based investigations. Narrative synthesis was conducted following the framework proposed by Popay et al. (2006), involving study coding, thematic grouping, and cross-study comparison. Six recurring instructional themes emerged across the reviewed literature: explicit instruction, the Concrete-Representational-Abstract (CRA) approach, schema-based instruction, structured practice interventions, technology-supported instruction, and cooperative or inclusive instructional strategies. Across studies, effective interventions consistently incorporated structured guidance, visual representations, scaffolded learning opportunities, repeated practice, and active learner engagement. Beyond improving arithmetic performance, these approaches appeared to support learners’ ability to interpret, understand, and apply numerical information in meaningful contexts. Overall, the findings suggest that effective mathematics instruction contributes not only to mathematical achievement but also to the development of functional numeracy literacy among students with intellectual and developmental disabilities. Further research employing more rigorous designs, larger samples, and longer follow-up periods is needed to strengthen the evidence base and examine long-term functional outcomes.