Problem posing is a challenging task for naive students.For problem posing,students must identify knowledge and procedures for solving problems.We suppose that understanding of procedural knowledge for problem solving enhances problem-posing activities.We developed a learning environment wherein students find and formally describe various types of procedural knowledge while problem-solving.The system comprises two modules: the knowledge editor and the problem-solving simulator.Students externalize a procedural knowledge set for solving crypt-arithmetic tasks using the knowledge editor.With the problem-solving simulator,they also simulate the behavior of the model comprising the knowledge set.The practice in class confirmed that two-thirds of the participants constructed reasonable models with our system.They appeared to succeed in identifying and externalizing procedural knowledge for solving a relatively complex arithmetic task.