Eksplorasi Etnomatematika Pada Kegiatan Arisan PKK Dan Dasawisma Di Kasihan Bantul

Ethnomathematics practices are frequently embedded within social activities without being realized, such as in the tradition of arisan (rotating savings and credit association). This study aims to explore and describe the mathematical concepts inherent in the arisan activities of the PKK and Dasawisma groups in Sonopakis Hamlet, Kasihan District, Bantul. A descriptive qualitative method with an ethnographic approach was employed. Data were collected through in-depth interviews with administrators and members, direct observation, and documentation of cash records. The results indicate that arisan activities distinctly embody social arithmetic and probability concepts. Social arithmetic concepts are identified in the management of mandatory contributions, voluntary savings, and the calculation of a 2% simple interest rate in the household goods procurement scheme. Meanwhile, theoretical and conditional probability concepts are represented through a lottery drawing mechanism without replacement for 33 members (selecting 3 names per meeting), where each member's initial probability of being drawn is P(A) = 3/33 = 1/11 (9.09%) and increases in subsequent drawings as the remaining pool decreases. These findings demonstrate that the local wisdom of arisan in Bantul holds significant potential as a contextual mathematics learning resource for school students.