Contents lists available at ScienceDirect Research in Developmental Disabilities journal homepage: www.elsevier.com/locate/redevdis Research Paper Using the virtual-abstract instructional sequence to teach addition of fractions Emily C. Bouck a, ⁎ , Jiyoon Park a , Jessica Sprick a , Jordan Shurr b , Laura Bassette c , Abbie Whorley d a Michigan State University, United States b Central Michigan University, United States c Ball State University, United States d Portland Public Schools, United States ARTICLE INFO Keywords: Mild intellectual disability Mathematics Single case Fractions ABSTRACT Background/aims/methods: Limited literature examines mathematics education for students with mild intellectual disability. This study investigated the effects of using the Virtual-Abstract in- structional sequenceto teach middle school students, predominantly with mild intellectual dis- ability, to add fractions of unlike denominators. Researchers used a multiple probe across par- ticipants design to determine if a functional relation existed between the Virtual-Abstract instructional sequence strategy and students’ ability to add fractions with unlike denominators. Procedures/outcomes: The study of consisted of three-to-nine baseline sessions, 6–11 intervention sessions, and two maintenance sessions for each student. Data were collected on accuracy across five addition of fractions with unlike denominators problems. Results/conclusions: The VA instructional strategy was effective in thestudents to add fractions with unlike denominators; a functional relation existed between the VA instructional sequence and adding fractions with unlike denominators for three of the four students. Implications: The Virtual-Abstract instructional sequencemay be appropriate to support students with mild intellectual disability in learning mathematics, especially when drawing or re- presenting the mathematical concepts may prove challenging. What this paper adds This papers adds to the limited literature examining mathematics education for students with mild intellectual disability as well as to the limited literature examining fraction instruction for this population as well as students with disabilities more generally. This paper also presents an alternative instructional sequence to the evidence-based Concrete-Representational-Abstract (CRA) instruc- tional sequence. 1. Introduction Fractions are considered an essential mathematical domain for students (National Mathematics Advisory Panel [NMAP, 2008]; Shin & Bryant, 2015). Procedural and conceptual knowledge of fractions are important for both understanding more advanced mathematical concepts in domains such as algebra, and for participating in daily activities such as cooking and personal finance (Jordan, Hansen, Fuchs, Siegler, Gersten, & Mickos, 2013; NMAP, 2008). The NMAP (2008) recommended students in middle school http://dx.doi.org/10.1016/j.ridd.2017.09.002 Received 21 June 2017; Received in revised form 21 August 2017; Accepted 4 September 2017 ⁎ Corresponding author. E-mail address: ecb@msu.edu (E.C. Bouck). Research in Developmental Disabilities 70 (2017) 163–174 0891-4222/ © 2017 Elsevier Ltd. All rights reserved. MARK