The objective of this work is to propose experimental activities, based on the History of Mathematics, that problematize the content taught in the 9th grade of elementary school, based on their historical production processes, provoking a dialogue between two approaches that underlie the present study: the history of mathematics and teaching by experimental activities. We believe that this dialogue enables the achievement of important specific objectives: humanization of mathematics enabling students of this school year to understand mathematics as a product of human need and meaning of mathematics promoting learning through the development of practical activities that bring meaning and motivation to learn new knowledge. Three traditional contents that appear in the curriculum of this segment are presented based on the simultaneous combination of these approaches: the Tales theorem, the Pythagorean theorem and the 2nd degree equation. For each of them, we present a historical approach, raise important reflections on constructions and authorship and suggest activities based on the dialogue between history and practice as proposals to be developed together with the students.