Mathematics is considered a difficult subject by most students. Material number reduction is more difficult to understand than addition, especially reduction of numbers with borrowing techniques. Learning outcomes related to understanding the concept of reducing numbers with borrowing techniques are included in the low category, as well as independent attitudes, and student learning motivation is also low. Therefore, researchers conducted corrective actions by applying realistic mathematics. This study aims to: (1) describe the process of implementing realistic mathematics, (2) analyze the process of developing independent attitudes, (3) analyze the process of developing learning motivation, and (4) analyze the development of learning outcomes. This study used the action research method, carried out through 3 cycles in class I B SD Tarakanita 1, Jakarta, with subjects as many as 33 students. Data were collected through observation, written tests, interviews, field notes, and analyzed descriptive qualitatively. The results showed: (1) corrective actions carried out in accordance with realistic mathematical steps, (2) an increase in understanding of the concept of reducing numbers more than ten with borrowing techniques, (3) an increase in independent attitude in each cycle, (4) increased learning motivation in every cycle. / Pelajaran matematika dianggap sebagai mata pelajaran yang sulit oleh kebanyakan siswa. Materi pengurangan bilangan lebih sulit dipahami dibandingkan penjumlahan, terlebih pengurangan bilangan dengan teknik meminjam. Hasil belajar berkaitan dengan pemahaman konsep pengurangan bilangan dengan teknik meminjam termasuk kategori rendah, demikian juga dengan sikap mandiri, dan motivasi belajar siswa pun rendah. Oleh karena itu, peneliti melakukan tindakan perbaikan dengan menerapkan matematika realistik. Penelitian ini bertujuan: (1) mendeskripsikan proses implementasi matematika realistik, (2) menganalisis proses perkembangan sikap mandiri, (3) menganalisis proses perkembangan motivasi belajar, dan (4) menganalisis perkembangan hasil belajar. Penelitian ini menggunakan metode PTK, dilaksanakan melalui 3 siklus di kelas I B SD Tarakanita 1, Jakarta, dengan subyek sejumlah 33 siswa. Data dikumpulkan melalui observasi, tes tertulis, wawancara,catatan lapangan, dan dianalisis secara deskriptif kualitatif. Hasil penelitian menunjukkan: (1) tindakan perbaikan dilakukan sesuai dengan langkah-langkah matematika realistik, (2) terjadi peningkatan pemahaman konsep pengurangan bilangan lebih dari sepuluh dengan teknik meminjam, (3) terjadi peningkatan sikap mandiri setiap siklus, (4) terjadi peningkatan motivasi belajar setiap siklus.