.
The number of all possible arrangements of 18 CDs is the number of all permutations of 18 items, i.e.
18! = 1*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18.
Only one of these permutations is in alphabetical order.
Therefore, the probability that the rack ends up in alphabetical order is equal to
P = . ANSWER
To get the numerical value, use a calculator.
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On Permutations, see introductory lessons
- Introduction to Permutations
- PROOF of the formula on the number of Permutations
- Problems on Permutations
- OVERVIEW of lessons on Permutations and Combinations
in this site.
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Combinatorics: Combinations and permutations".
Save the link to this textbook together with its description
Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson
into your archive and use when it is needed.