This article aims to examine how transformations through conversion contribute to the different semiotic representation registers—mother tongue, algebraic register, numerical register, fractional register, percentage, and decimal—in the processes of teaching and learning mathematical objects. The starting point involved the design and development of activity sequences based on problem situations from the students’ reality, sparking discussions within the scope of Critical Financial Education. Data analysis was grounded in the Theory of Semiotic Representation Registers. The results reveal gaps in students’ learning when performing certain calculation procedures and in their written communication. Furthermore, the findings suggest that aligning Financial Education with Mathematics teaching creates favorable conditions for students to construct mathematical knowledge, fostering the development of critical, autonomous citizens capable of responding to social contradictions.