SOLUTION: What is the probability that if 11 letters are typed, no letters are repeated? The probability that no letters are repeated is

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Question 1199902: What is the probability that if 11 letters are typed, no letters are repeated?
The probability that no letters are repeated is

Answer by ikleyn(52915) About Me  (Show Source):
You can put this solution on YOUR website!
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What is the probability that if 11 letters are typed, no letters are repeated?
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We have 26 lowercase letters and 26 uppercase letters in English alphabet.


Assuming that we use lowercase letters only, there are  26%5E11 possible words 
of the length 11.


Of them, the number of words with no repeating letters is  26*25*24*23*22*21*20*19*18*17*16
(11 factors of integer numbers in descending order starting from 26, in all).


The probability do not have repeating letters is


    1 -  = 


    = 1 - 0.084026 = 0.915974   (rounded).    ANSWER

Solved.

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A TWIN problem to it is a popular problem on finding the probability
that there is no coinciding birthdays in the group of 11 persons.

See the lesson
    - Coinciding birthdays
in this site.