Twenty-two Foolish Primes
Problem 239Published on Friday, 3rd April 2009, 05:00 pm; Solved by 1182; Difficulty rating: 65%
A set of disks numbered 1 through 100 are placed in a line in random order.
What is the probability that we have a partial derangement such that exactly 22 prime number discs are found away from their natural positions?
(Any number of non-prime disks may also be found in or out of their natural positions.)
Give your answer rounded to 12 places behind the decimal point in the form 0.abcdefghijkl.