Final answer:
The constant of proportionality in the equation b = 1.25c is 1.25.
Step-by-step explanation:
The constant of proportionality in the equation b = 1.25c is 1.25.
In a proportional relationship, the constant of proportionality represents the ratio between the two variables. In this equation, for every unit increase in c, there is a corresponding increase of 1.25 in b. For example, if c is 2, then b is 2.5.