In distance learning for computer literacy, a student's skill is dependent on personal experience. In such cases, it is important to determine the student's understanding. In order to determine the level of understanding, it is necessary to clarify the hidden relationships among the concepts involved in a problem. We think it is possible to determine the understanding correctly by subdividing concepts and by subdividing problems. In this paper, we propose the following method; first we divide a problem conceptually into some questions; next we ask those questions of students step by step; finally we build a conceptual model of the problem using the rate of correct answers.