Mathematics is a science that deals with the study of abstract forms so that it requires objects or visual aids to concretize them to become more tangible and clear. Science and technology has developed rapidly in education, one of which is an android-based learning media. The purpose of this study was to develop an Android-based learning media on mathematics specifically in the form of algebraic for students in grade VII of SMP Negeri 2 Kartasura. Furthermore, after the development, the validity and feasibility tests were conducted by media experts, material experts, learning practitioners and students. This research conducted by Research and Development (R&D) method. In its development, 6 stages must be passed namely the analysis phase, the planning phase, the development phase, the verification phase, the validation phase, and the final phase with the learning media called OBAR. The developed media was feasible with the result of validation from media experts obtaining an average score of 3.94, was valid. The result of the validation from material experts obtained an average score of 4.5, was very valid. The results of validation by learning practitioners obtained an average score of 4.2, was valid. Moreover, the validation of the students’ responses obtained an average score of 4.54, was most feasible category.

Penelitian ini bertujuan untuk mendeskripsikan proses penalaran aljabar siswa sebagai hasil dari pelaksanaan pembelajaran problem based learning (PBL) dalam pembelajaran matematika. Jenis penelitian ini adalah menggunakan metode kualitatif dengan subjek penelitian 3 orang siswa yang diambil dari 27 siswa kelas VII B SMP N 2 Ambarawa. Data hasil penelitian dianalisis dengan mendeskripsikan kemampuan penalaran aljabar siswa sesuai dengan indikator dan tingkat level penalaran siswa pada pembelajaran matematika. Teknik pengumpulan data yang dilakukan dengan observasi, tes dan dokumentasi. Hasil penelitian ini menunjukkan bahwa pembelajaran matematika menggunakan model (PBL) tingkat kemampuan penalaran aljabar siswa pada kemampuan tinggi mampu mengenal pola, mencari pola, dan menggeneralisasikan pola. Siswa kemampuan sedang tidak dapat menggeneralisasikan pola tetapi mampu mengenal dan mencari pola. Siswa kemampuan rendah hanya mampu mengenal pola.Kata kunci : Pembelajaran matematika, penalaran aljabar, problem based learning