For college and university level advanced Mathematics
What if we have a disk centered at $(0,0)$ of radius $r$, and another one centered at $(\epsilon,2r+\epsilon)$ for sufficiently small $\epsilon$, and so on? Then we can have a disk with centre at every possible real distance along the $x$ axis. This is what I meant previously.
"Everything should be made as simple as possible, but not simpler." - Albert Einstein