Solution
The price is the dependent variable
The amount of coffee is the independent variable
The constant of proportionality:
When two variables are directly or indirectly proportional to each other, then their relationship can be described as y = kx or y = k/x, where k determines how the two variables are related to one another. This k is known as the constant of proportionality.
For this problem, As the amount increases, Price increases as well. This is a direct variation scenario.
Thus, We can say
Thus, the constant of proportionality = 7.5