In this paper, we examine the implementation of a Japanese teacher educators' lesson, where he applies and, at the same time, inform the students about "structured problem solving". We describe a specific lesson titled "Quantity and Measurement" for elementary school teacher students and we show how the educator make the students aware of the didactic transposition of the material and how he makes the students experience and learn about applying "structured problem solving" in practice. We also show how the Japanese curriculum influences the scale of the mathematical praxeology to be learned and how the students are given opportunities to develop their insight into the PCK during their education in mathematics.