Resumen:
This paper examines the arithmetic of digit sums in the teaching and learning process in elementary and high school. The arithmetic of digit sums is equivalent to the arithmetic modulus 9, with the difference being the number 9 with remainder 0. We create patterns (geometric figures) with the sums of digits, with the help of GeoGebra. We also show that some figures can be made on graph paper. Although teaching patterns is a challenge for teachers, this paper aims to share the methodology adopted in order to contribute with practical experience in teaching algebra in the classroom. Keywords: Sum of digits, Patterns, GeoGebra.
