The objectives of the study were to develop valid and practical problem based learning of students' worksheet for junior high school in Lubuklinggau. This is developmental study  which formative research type applied. The subject of the research was 75 junior high school students of Lubuklinggau city consists of 27 students of SMPN 9 Lubuklinggau, 27 students of SMPN 11 Lubuklinggau, 21 students of SMP PGRI Lubuklinggau. Walk through was used in data collection to know the construct, content and language validities of students' worksheet; document to know the practicality of students' worksheet. This research produced problem based learning students' worksheet which measure the students' mathematic reasoning ability. The result of mathematic reasoning ability test was 70.15. In summary, developing students' worksheet has potential effect toward students' mathematic reasoning ability. Keywords: Worksheet (LKS), problem based learning, reasoning ability

Masih rendahnya pemahaman siswa tentang operasi bilangan bulat menyebabkan para siswa mengalami kesulitan dalam menyelesaikan soal operasi bilangan bulat yang terkait dengan konsep dan prinsip matematika. Penelitian ini bertujuan untuk menganalisis tahap kesulitan siswa dan penyebab kesulitan siswa kelas V SD Negeri 15 Curup dalam menyelesaikan soal-soal operasi bilangan bulat. Jenis penelitian ini adalah penelitian deskriptif kualitatif. Pengumpulan data dilakukan dengan metode tes, kuesioner, wawancara dan dokumentasi. Berdasarkan hasil penelitian dan analisis data dapat disimpulkan bahwa tahap-tahap kesulitan siswa kelas V SD Negeri 15 Curup dalam menyelesaikan operasi bilangan bulat adalah kesulitan fakta 76,8%, kesulitan konsep 76,8%, kesulitan operasi 79,4%, dan kesulitan prinsip 79,4%. Faktor-faktor penyebab siswa kesulitan dalam menyelesaikan operasi bilangan bulat yaitu : 1) siswa kesulitan dalam menuliskan penjumlahan bilangan bulat dan menggambar pada garis bilangan. 2) siswa belum memahami konsep operasi pengurangan dan campuran bilangan bulat. 3) siswa kesulitan menentukan hasil dari pengurangan bilangan bulat, kurang teliti, tidak paham maksud soal. 4) siswa kesulitan membuat model matematika dari soal cerita, kesulitan menyatakan nilai operasi campuran dan belum menguasai materi operasi bilangan bulat

Reasoning ability is very important to note because it is able to train students’ thinking activities to be able to solve mathematical problems. This ability is also a benchmark in determining student achievement in the field of mathematics, one of which is in the international event TIMSS and PISA. However, the competitiveness of Indonesian students is still very low compared to other countries. This can be caused by the lack of giving questions that practice the ability of reasoning by the teacher. Therefore, there is a need for improvement in the process of learning mathematics. In the learning process, students should be given the opportunity to explore all their potential. The teacher can offer problems that are able to train and develop mathematical reasoning abilities. Problem-based learning is problem-centered learning. Problems given can be related to real-life students and can practice the ability to reason and solve mathematical problems.

The purpose of this study was to develop a realistic worksheet using the Ethnomatematics on SPLDV material and to determine the quality of worksheets in terms of validity and practicality. The method used in this study is the Research and Dependency (R&D) method which is a developmental study referring to the 4-D development model, namely define, design, develop, and disseminate modified to 3-D. The instruments used to measure the quality of worksheets that were developed include validation sheets, and practicality questionnaires. The product of this research is a realistic worksheet using ethnomatematics context on SPLDV material with the advice of eighth grade students of junior high school. The results showed that: (1) the quality of worksheets seen from the validity aspects included in the valid category with an overall average score of 3.06; and (2) the quality of worksheets seen from the practical aspect is categorized very practical with an overall average score of 3.5. Conclusion, the development of PMRI-based worksheets in the context of ethnomatematics in SPLDV material was declared valid and practically used by students. Keywords: Ethnomatematics worksheet, PMRI, SPLDV