Penelitian ini bertujuan untuk mendeskripsikan berpikir kombinatorial siswa SMA dengan kategori kemampuan matematika tinggi, sedang, dan rendah dalam menyelesaikan masalah kombinatorik. Berpikir kombinatorial merupakan kemampuan berpikir dasar yang harus terus dikembangkan menuju kemampuan dan keterampilan berpikir kritis. Untuk meningkatkan hal itu, pembelajaran dan penugasan harus berorientasi pada masalah. Masalah yang digunakan pada penelitian ini adalah masalah kombinatorik. Penelitian ini merupakan penelitian deskriptif dengan menggunakan pendekatan kualitatif. Subjek penelitian terdiri dari tiga siswa yang berumur 16 tahun dan telah mempelajari materi peluang kelas X serta berkemampuan matematika tinggi, sedang, dan rendah. Data pada penelitian ini diperoleh melalui tugas masalah kombinatorik, dan wawancara berbasis tugas. Data yang diperoleh dianalisis dengan mereduksi data, menyajikan data, dan menarik kesimpulan. Hasil penelitian menunjukkan bahwa: (a) berpikir kombinatorial siswa berkemampuan tinggi dimulai dari formulas/expressions → counting processes → sets of outcomes → expressions → counting processes → sets of outcomes → counting processes → sets of outcomes yang didalamnya memenuhi semua indikator tingkat berpikir kombinatorial dan menggunakan dua jenis strategi verifikasi, (b) berpikir kombinatorial siswa berkemampuan sedang dimulai dari expressions → sets of outcomes → formulas → counting processes → sets of outcomes → counting processes → sets of outcomes yang didalamnya memenuhi semua indikator tingkat berpikir kombinatorial dan menggunakan satu jenis strategi verifikasi, (c) berpikir kombinatorial siswa berkemampuan rendah dimulai dari expressions → sets of outcomes → counting processes → sets of outcomes yang di dalamnya terpenuhi sebagian indikator tingkat berpikir kombinatorial dan tidak menggunakan strategi verifikasi.

This research aims to describe the combinatorial thinking of high school students with high, medium, and low math ability categories in solving combinatoric problems. Combinatorial thinking is a basic thinking ability that must be continuously developed towards critical thinking abilities and skills. To enhance that, learning and assignments must be problem oriented. The problem used in this study is a combinatoric problem. This research is a descriptive study using a qualitative approach. The research subjects consisted of three 16-year-old students who had studied probability material for class X and had high, medium, and low mathematical abilities. The data in this study were obtained through combinatoric problem assignments and task-based interviews. The data obtained will be analyzed by reducing data, presenting data, and drawing conclusions. The results of the study show that: (a) high-ability students' combinatorial thinking starts from formulas/expressions → counting processes → sets of outcomes → expressions → counting processes → sets of outcomes → counting processes → sets of outcomes which fulfills all indicators of the level of combinatorial thinking and using two types of verification strategies, (b) medium-ability students' combinatorial thinking starts from expressions → sets of outcomes → formulas → counting processes → sets of outcomes → counting processes → sets of outcomes which fulfills all indicators of the level of combinatorial thinking and uses one type of verification strategy, (c) low-ability students' combinatorial thinking starts from expressions → sets of outcomes → counting processes → sets of outcomes in which some indicators of the level of combinatorial thinking are met and do not use verification strategies.