P239
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Twenty-two Foolish Primes

ℹ️Published on Friday, 3rd April 2009, 05:00 pm; Solved by 2020;
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.



Soluzione

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