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Prime Nine

Probability puzzles require you to weigh all the possibilities and pick the most likely outcome.

 

Puzzle ID:#40004
Fun:*** (2.56)
Difficulty:** (1.97)
Category:Probability
Submitted By:RampaginRoboAgb*****!

 

 

 



There are 9! ways to arrange the digits 1-9 to form a 9-digit number.

E.g. 345, 987, 126

If you know this, then if I wrote all 9! possibilities on cards (1 way per card), and I asked you to select one at random; what is the probability that the number you selected is prime?


Hint

Divisibility tricks are useful now.
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