The Numerical Ability of students in elementary schools which is very low can occur because it is caused by choosing learning models and media that are not suitable for students' abilities. This study aims to determine student development under the influence of the Problem Based Learning learning model using learning videos on YouTube. In addition, this study also aims to determine the numeracy skills of elementary school students in the implementation of the learning process by selecting the Problem Based Learning learning model. This study uses a quantitative method with the type of experiment. The population in this study were all grade 5 students at SDN Wonosunyo II Gempol. Students watch learning videos on YouTube and then work together with their peers and look for problems that exist in everyday life. Students get student worksheets which are then worked on and then presented in front of the teacher and their peers. The material used in this research is fractional operations. The results of this study are that students are interested in interesting learning, but there are also some students who are bored when shown YouTube videos that are shown on laptops. Meanwhile, the learning of numeracy is carried out using effective media, so that it can arouse students' enthusiasm for learning and the development of students' numeracy in elementary schools has improved and is running well.