ABSTRAK
Tujuan penelitian ini adalah untuk meningkatkan pemahaman konsep Pecahan dengan menggunakan model Realistic Mathematics Education bagi siswa kelas 3 SD Negeri Karangasem III No. 181 Surakarta Tahun Ajaran 2014/2015.
Bentuk penelitian ini adalah Penelitian Tindakan Kelas (PTK) sebanyak dua siklus dan tiap siklus berlangsung selama dua pertemuan. Tiap siklus terdiri dari empat tahapan yaitu perencanaan, tindakan, observasi dan refleksi. Subyek penelitian ini adalah guru dan siswa kelas 3 SD Negeri Karangasem III No. 181 Surakarta Tahun Ajaran 2014/2015 yang berjumlah 27 siswa. Teknik pengumpulan data yang digunakan adalah dokumentasi, observasi, wawancara dan tes. Uji validitas menggunakan triangulasi sumber dan validitas data. Teknik analisis data yang digunakan adalah model analisis interaktif (Miles&Huberman) yang terdiri dari tiga komponen yaitu reduksi data, sajian data dan penarikan simpulan (verifikasi).
Hasil penelitian menunjukkan bahwa pemahaman konsep siswa tentang pecahan meningkat. Hal itu terlihat dari nilai setiap siklus yang meningkat. Nilai rata-rata sebelum tindakan (prasiklus) 56,29, pada siklus I nilai rata-rata menjadi 69,67, dan pada siklus II meningkat menjadi 81,9. Sebelum dilaksanakan tindakan (prasiklus), Siswa yang mencapai standar ketuntasan sebanyak 9 orang (33%), siklus I sebanyak 15 orang (56%), dan pada siklus II sebanyak 24 siswa (89%).
Berdasarkan data tersebut, dapat disimpulkan bahwa penggunaan model Realistic Mathematics Education dapat meningkatkan pemahaman konsep pecahan bagi siswa kelas 3 SD Negeri Karangasem III No. 181 Surakarta Tahun Ajaran 2014/2015.
Kata Kunci : Model Realistic Mathematics Education, Pemahaman Konsep, Pecahan.  
ABSTRACT
The purpose of this research is to improve concept understanding of fractions by applying Realistic Mathematics Model on the third grade students in SD Negeri Karangasem III No.181Surakarta period 2014/2015.
The type of this research is classroom action research (CAR), it consists of 2 cycles and each cycle was held in two-times learning. Each cycle consists of four phases, they are planning, action, observation, and reflection. The subject of this research are the teacher and the third grade students in SD Negeri Karangasem III No. 181 Surakarta period 2014/2015, which consists of 27 students. The data collecting techniques are documentation, observation, interview, and test. The data validity is examined by using source triangulation and data data validity. The data analysis technique is interactive analytic model (Miles&Huberman) which consists of three elements, they are data reduction, data display, and conclusion drawing (verification).
The result of this research shows the improvement of students concept understanding of magnet force. It is shown by the grades of each cycle, the average grade before the action (pre cycle) was 56,29, in the first cycle the average grade increased to 69,67, and in the second cycle the average grade increased to 81,9. Before the action was held (pre-cycle), the students who acquired passing grade (=70) were 9 students (33%), in the first cycle the students who passed were 15 students (56%), and in the second cycle the number of students who acquired passing grade increased to 24 students (89%).
Based on the data, it can be concluded that the application of Realistic Mathematics Education model can increase the concept understanding of fractions on the third grade students in SD Negeri Karangasem III No.181 Surakarta period 2014/2015.
Keywords : Realistic Mathematics Education, Concept Understanding, Fractions.