You know that is a 95424250944 digit number. Consider the set . How many of these numbers start with a 9? (Example: 91 starts with a 9, but 729 does not start with a 9). (Obviously you are not allowed to use a computer. That's why the number is bloated up by so much that even a computer can't feasibly solve it).
Source: One of the practice problems from the Indian National Mathematics Olympiad training programme.