Indonesia has many gifted young scientists, who need to get support and good opportunities to work. Numerical ability is one element that must be mastered in mathematics. This study aims to determine the effect of numerical ability of students who take part in learning using the Team Assisted Individualization (TAI) learning model with those who follow conventional learning models. The type of research is quasi experimental design. The instrument used to test numerical ability on the topic of sequences and series is an essay. Data were analyzed from the results of the posttest using t-test. Based on the calculation, obtained that tcount of 3,977 and ttable of 2,005, it can be concluded that ttable = table means that the Team Assisted Individualization (TAI) learning model has a good impact on the numerical ability of students.