Suppose $$r^{}_{}$$ is a real number for which $$\left\lfloor r + \frac{19}{100} \right\rfloor + \left\lfloor r + \frac{20}{100} \right\rfloor + \left\lfloor r + \frac{21}{100} \right\rfloor + \cdots + \left\lfloor r + \frac{91}{100} \right\rfloor = 546.$$ Find $$\lfloor 100r \rfloor$$. (For real $$x^{}_{}$$, $$\lfloor x \rfloor$$ is the greatest integer less than or equal to $$x^{}_{}$$.)

(第九届AIME1991 第6题)