此页面是2024-2025年度美国 Math League 思维探索第二阶段活动试题 FAQ (常见问题)。 我们会随时更新页面内容。

第二阶段的题目有这么多，打印出来几十页，该怎么入手呢? 至少有两种策略。一种是每天做一点，比如每天花20 – 30分钟。 还有一种策略是平时不做，等周末安心坐下来，心无旁骛，花3个小时专心做题。 这两种策略哪种更有效呢? 因人而异，没有绝对的好坏。但是我们觉得对大多数人来说， 第一种策略(即每天花20 – 30分钟)会更有效。大家可以试试。

Let's assume John's age is 3. Then, the ages of his three cousins could be 7, 17, and 23 or 11, 17, and 19. Since there are multiple possibilities, the answer is not unique, making it ambiguous. Therefore, John's age cannot be 3.

Now, let's assume John's age is 7. The ages of his three cousins could be 3, 17, and 23 or 7, 13, and 23. Again, there are multiple valid sets, making it ambiguous. So, John's age cannot be 7 either.

Your task is to find an age for John where the set of his cousins' ages is unique, eliminating any ambiguity.