Addition is one of the foundational math skills students with mild intellectual disabilities need before moving on to more advanced concepts. At SLB Bina Bangsa Padang, a student was observed struggling with addition problems involving numbers 1–10, answering only four out of ten questions correctly. This study set out to find whether a counting-car board could raise the addition ability of a fourth-grade student with mild intellectual disabilities at SLB Bina Bangsa Padang. The researchers took a quantitative approach through a Single Subject Research (SSR) A–B design, with one fourth-grade student with a mild intellectual disability as the participant. Data came from addition-skill tests given at each session and were then read visually, both within and across conditions. During baseline, the student's score held steady at 40%. Once the intervention began, scores climbed step by step On average, the student's ability rose from 40% to 76%, confirming that the counting-car board helped strengthen addition skills in a student with mild intellectual disabilities.

Kemampuan berhitung penjumlahan menjadi fondasi matematis yang wajib dikuasai murid disabilitas intelektual ringan sebelum melangkah ke konsep matematika lanjutan. Hasil observasi di SLB Bina Bangsa Padang memperlihatkan seorang murid belum bisa mengerjakan soal penjumlahan bilangan 1–10 dengan baik — dari 10 soal yang diberikan, hanya empat yang terjawab benar. Penelitian ini menguji apakah media papan mobil hitung mampu mendongkrak kemampuan penjumlahan bilangan 1–10 pada murid disabilitas intelektual ringan kelas IV SLB Bina Bangsa Padang. Peneliti memakai pendekatan kuantitatif melalui metode Single Subject Research (SSR) dengan desain A–B. Subjeknya seorang murid kelas IV penyandang disabilitas intelektual ringan. Data diambil lewat tes kemampuan penjumlahan di setiap sesi pertemuan, lalu dibaca secara visual baik dalam satu kondisi maupun antar kondisi. Pada fase baseline, kemampuan subjek bertahan di angka 40%. Selama fase intervensi, angka ini naik bertahap. Rata-rata kemampuan subjek terangkat dari 40% menjadi 76%. Media papan mobil hitung terbukti efektif mendongkrak kemampuan penjumlahan bilangan 1–10 pada murid disabilitas intelektual ringan.