Final answer:
The equation to find the Constant of Proportionality is Y = kx, which represents a direct proportion between two variables where y changes by the same rate as x.
Step-by-step explanation:
The equation used to find the Constant of Proportionality is C) Y = kx. When two values are directly proportional, we express their relationship with the formula y = kx, where y is the dependent variable, x is the independent variable, and k is the Constant of Proportionality, which defines the ratio of the dependency between the two variables. This equation implies that as x increases, y increases by the same proportion, which is determined by the k value. If we were to graph this relationship, the result would be a straight line that passes through the origin (0, 0).