Examining the effect primary school teachers' preferred teaching method has on primary school students' mathematics achievement is important. In this context, the purpose of the research is to determine whether the worked example method is effective on students' ability to learn fundamental knowledge about fractions and their success in solving mid- and highdifficulty fraction problems compared to the traditional teaching method. The research uses the experimental design with a pretest-posttest control group. The experimental group has 36 students, and the control group has 37 students. While teaching fractions was conducted in accordance with the traditional teaching method in the control group, the worked example method was applied in the experimental group. The research results from the research determined the worked example method to be more effective than the traditional teaching method in learning the fundamental knowledge about fractions and developing student success in solving mid- and high-difficulty fraction problems. The traditional teaching method was not effective at developing students' success in solving high-difficulty fraction problems. Because problem solving is a skill that develops slowly, teachers should not prefer time-consuming methods in developing problem-solving skills. Using the worked example method is suggested in primary school as it has been revealed to develop problem-solving skills in a short time and these skills' foundations are laid in primary school.