Realistic Mathematics approach is a theory of learning and teaching in the mathematical approach. This theory was first introduced and developed in the Netherlands in 1970 by the Freudenthal Institute. In case this is a realistic mathematical school mathematics conducted by putting reality and experiences of students as a starting point of learning, realistic problems are used as a source of the emergence of concepts of mathematics or formal mathematical knowledge. According to Freudenthal (Asmin, 2003:2) view that mathematics should be linked to the real thing for students and should be viewed as a human activity. View of the above, in line with what is disclosed Soedjadi (Asmin, 2003:3) that the Realistic Mathematics Educations (RME) has a basic philosophy is that "mathematics is a human activity," and no longer considered "ready". This philosophy resulted in a very fundamental changes about the process of learning mathematics. No longer just the provision of information in learning mathematics, but it must transform into a human activity to acquire knowledge of mathematics. Furthermore, Soedjadi (Asmin, 2003:3) suggests there are three principles that have realistic mathematical approaches, namely: Reinvention and progressive matematization, didactical phenomenology and self-developed models. The intention is to start from a real phenomenon or event for the students, the principle of Freudenthal didactical phenomenology that learning should start from a contextual problem that ultimately led to a mathematical concept is learned must be used. Furthermore, using the principle of guided reinvention through progressive mathematizations, students led a didactic and efficiently from one level to the next level of thinking through matematisasi and use of self developed models which means that in learning math concepts, students develop their own models or ways -how itself solve the problem by supporting armed with the knowledge that has been owned. RME above three principles, according to Gravemeijer (Asmin, 2003:3) operationalized into five basic characteristics of the Realistic Mathematic's Education (RME).
The five distinctive characteristics of realistic mathematics mentioned above is to use the context of "real world", models, production and construction students, interactive, and linkages (intertwinment) (Suherman, et al 2001:128). In realistic mathematics learning, according to De Lange (Suharta, 2007:3) says that learning begins with a contextual or real-world problems, thus allowing students to use previous experience directly. Search process (core) of the corresponding concept of the real situation, according to De Lange (Suharta: 2007:3) expressed as a conceptual matematisasi. Through abstraction and formalization of the students will develop a more comprehensive concept. Then students can apply math concepts to a new field of the real world. Therefore, to bridge the mathematical concepts with everyday experiences children need to be considered matematisi everyday experience (mathematization everyday experience) and the application of mathematics in everyday life. Use of these models is a bridge for students from the real situation to situation or from abstract mathematics informal to formal mathematics. This means that students create their own model in solving the problem. In this case, making "free production" students are encouraged to reflect on what they consider important part in the learning process. Informal strategies of students in the form of a contextual problem-solving procedure is a source of inspiration in the development of further learning is to construct a formal mathematical knowledge. Interaction between students and teachers are essential in realistic mathematics approach. Explicit forms of interaction in the form of negotiation, penjelasasn, justification, agree, disagree, question or reflection is used to achieve the formal form of an informal student. In realistic mathematics learning, integrating units of mathematics is essential. If we ignore learning linkages with other fields, it will have an effect on problem solving. In applied mathematics, usually requires a knowledge of more complex, and not only arithmetic, algebra, or geometry but also in other fields.
The five characteristics of learning and teaching according to the above philosophy of 'realism' is a soul in every activity of learning mathematics (Suherman, et al 2001:128). So, in the implementation of learning mathematics using realistic mathematical approach should seek to applying the five principles above.