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Every year the labour demonstration in the industry area has always been the fundamental problem of a developing country, Indonesia is no exception. Some mathematics present regarding the labour issue. In order to excavate mathematical concepts from the setting, an auto|ethnographical study was conducted by the teacher and the researcher. Emerging mathematical concepts that are found often, was developed to design a set of mathematical activities. The learning design was using Realistic Mathematics Education (RME) as a learning approach and Problem Solving Learning (PSL) is defined as the learning model. This study combines two research methodologies, which are auto|ethnography and design research. The results indicate that Hypothetical Learning Trajectory (HLT) which consists of several learning activities can help students understand the concept of calculation strategy on the material of the mixed counting operation.

counting strategy; hypothetical learning trajectory; auto|ethnography, design research