There is a well known video of a helicopter with 5 evenly spaced rotor blades where the rotor is synced with a digital camera's frame rate.
Assuming the camera is at 60 hertz (60 frames per second), the rotor must be spinning at x/5 * 60. Where it seems like x could be any integer. However, let's say x is 1. So the rotor is spinning at 12 hertz. It's quite possible that in actuality, it's spinning slower than that, so my equation of rotor rate = x/5*60 seems to be incorrect.
The reason is that given the footage, it's impossible to say if a single rotor is spinning all the way around, or just 1/5, or 3/5 around, etc. Or 8/5 around.
What is the description/name of the relationship between x and 60? It's not a factor is it?
Here's the original vid: https://www.youtube.com/watch?v=yr3ngmRuGUc
What you seem to be describing here is aliasing or folding where your system's frequency cannot be distinguished from another frequency that's reflected across the Nyquist Frequency.
But that's not $1/x$: if your sampling rate is, say, $60\text{Hz}$, your Nyquist frequency is $30 \text{Hz}$, and phenomena running at $25 \text{Hz}$ will have aliases at $60k - 25 = (35 + 60k)\text{Hz}$ and $(25 + 60k)\text{Hz}$.