This paper focuses on the effective learning to understand the transformation of equation about speed utilizing the RTMaC lesson study in the Japanese elementary school. In Japan， children activities in the school mathematics tend to be inclined to numerical calculation. Because of that， it is generally said that the children have less opportunities to understand various concepts of mathematics. This would be considerable issues of the children developing further mathematical thinking. One such example is the transformation of equation about speed. In response to this， we developed teaching materials and methods， and had the classroom practices. As a result， we confirmed that the teaching materials and methods elevate the students to understand the concept ， and it leads to the understanding of the transformation of equation about speed.