Formação triangular - I

Synopsis: Dorothy and Sandrinha should plan a presentation of Sete de Setembro, with their students, then the question arises of what kind of training present. At the suggestion of a math teacher they decide to do a triangular formation which will be divided into five other triangles. Therefore should examine the possibilities of how to distribute the students in these triangles. To solve this problem they use the knowledge of arithmetic progression. (Part 1/2)
Source: Unicamp - M3, Mathematics Multimedia.
URL: http://m3.ime.unicamp.br/recursos/1312