I have a question, I apologize if it seems trivial but I just want to make sure this is correct or be corrected if not. I have a function
$$f(r,x) = \dfrac{r}{x}$$
Where $r$ - is total revenue of purchases and $x$ is the number of customers who made a purchase on a website. Here is my question with an example:
Example: Say, I have $r = \$300$ from 10 customers, so $$f(300, 10) = 30$$
Now, I find that of my 10 customers two of them are purchasing from separate accounts. Ex: User1 is purchasing also as User 8 and User 2 is also purchasing as User 10. I have the same revenue but a different cohort size of 8 now.
$$f(300, 8) = 37.5$$.
I want to determine how much of an increase there is from $f(300, 8)$ to $f(300, 10)$.
My questions are:
Can I just perform a percent increase? $$\dfrac{(37.5 - 30)}{30}*100 = 25\%$$
If this is incorrect what is the correct way of comparing? This may seem trivial to some but I believe I'm being thrown off by the change in the denominator.
Thank you for any help or comments!