The equation y = kx represents a proportional relationship between x and y, where k is the constant of proportionality. for a moving object, the equation d = st represents a proportional relationship between distance (d) and speed (s) or between distance (d) and time (t). explain the different ways that you can define the constant of proportionality for this equation. then describe some other equations that represent proportional relationships in the real world and explain why they're useful.