Abstract: Although Vietnamese students are quite good in solving problems with given mathematical models or partially modeling, they feel difficult in creating their own mathematical models to solve non-routine realistic problems. Influenced by constructivism and connectivism, we will try to describe and give reliable data to analyze the potential of Vietnamese students in understanding concepts of core mathematical skills in solving realistic problems in meaningful contexts with the mathematics education integrated closed-open approach. This approach is really relevant to classroom mathematics teachers in implementing the lesson plans with the mathematics taxonomy of solving mathematics problems from closed to open: reproducing knowledge, applying regular procedure, complex procedure, without learned procedures, open ended. The results showed that realistic open problems with meaningful contexts created an active learning environment in the classroom and students make a cycle to understand mathematical concepts. The cycle includes three main steps from close to open through understanding: Proficiency in mathematical skills, understanding concepts and applying skills in solving open ended realistic problems.
Keywords: Solving realistic problems, closed-open approach.