# Solving inverse square of visible scale

I'm not super-adept in mathematics, so I turn to you for help. As I read, the perceived scale of an object reduces by the inverse square as the viewed distance increases. In order to solve for this, the inverse square formulas I've found require you to know the scale at some distance. Well, I only know the scale at distance zero, so I can't get the equation to work. How should I solve for this?

Here's the formula I'm attempting to use: Newton's Inverse Square Law

$$\frac{I_1}{I_2}=\frac{D_2^2}{D_1^2} \quad \rightarrow \quad I_2 = \frac{I_1 \times D_1^2}{D_2^2} \\ \quad OR \quad \\ \quad\\ NewSize = \frac{OrigSize \times OrigDistance}{NewDistance} \quad \rightarrow \quad 0 = \frac{10 \times 0}{5}$$

Edit: Now that I think more about it, the conundrum is that if my initial measurement is 10 units wide at the source (distance zero), I can't reduce it to 1/4 by doubling the distance because you can't double zero. Right? Am I even looking at the right equation?