11.2. In a box, there are white and blue balls, with the number of white balls being 8 times the number of blue balls. It is known that if you pull out 100 balls, there will definitely be at least one blue ball among them. How many balls are there in the box?
Answer: 108.

Solution: Since the number of white balls in the box is 8 times the number of blue balls, the total number of balls in the box is divisible by 9. Since 100 balls are drawn from it, the smallest possible number of balls in the box $n=108$, of which 12 are blue and 96 are white. Since there are fewer than a hundred white balls, there will be blue balls in any set of a hundred balls. If $n>108$, then $n \geq 117$ (since $n$ is divisible by 9). In this case, the number of white balls will be greater than or equal to 104, and there will be sets of a hundred balls that do not contain any blue balls.