Constant Proportionality

A narrated walkthrough, in Portuguese, of the constant of proportionality k. It opens on the name k, then builds a direct proportion (y = k·x, k = 2 reais por unidade) with a table whose quotient never changes and a straight line whose slope is k, then an inverse proportion (y = k/x, k = 8 horas de trabalho) whose product stays fixed while the graph falls as a curve, and closes by placing the two roles