An Unfair Die

An unfair 100 sided die is numbered from 1 to 100. The ratio of the probability of rolling $x$ to the probability of rolling $y$ is equal to the ratio of $x$ to $y$ . The unfair die is rolled twice. The probability of rolling a multiple of 3 at least once is $\frac{a}{b}$ . What are the last three digits of $a+b$ ?