if x = 25 results in y = 200, x = 100 so y = 50, x = 200 so y = 25 etc, what mathmatical formula does this give?

if x = 25 results in y = 200, x = 100 so y = 50, x = 200 so y = 25 etc, what mathmatical formula does this represent ?

$$x\cdot y = 5000$$

hyperbola:   $$y = \frac{5000}{x}$$