This study aimed to describe the proportional reasoning of prospective teachers and their predictions about students' answers. Subjects were 4 prospective teachers 7 th semester Department of Mathematics Education, Muhammadiyah University of Purworejo. Proportional reasoning task used to obtain research data. Subjects were asked to explain their reasoning and write predictions of student completion. Data was taken on October 15 th , 2014. Interviews were conducted after the subjects completed

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... e task and recorded with audio media. The research data were subject written work and interview transcripts. Data is analysed using qualitative analysis techniques. In solving proportional reasoning task, subjects using the cross product. However, they understand the meaning of the cross product. Subject also could predict students' reasoning on the matter.