Question 1184029
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Allowing for repetition, there are *[tex \Large 10^4] possible PINs, and therefore the probability of guessing in one try is *[tex \Large \frac{1}{10,000}]. If repetition is not allowed, then there are *[tex \Large 10\,\times\,9\,\times\,8\,\times\,7\ =\ 5040] possible PINs, and the probability of guessing on one try is *[tex \Large \frac{1}{5040}], slightly less than twice as likely as guessing if repetition is allowed.

																
John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
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From <https://www.algebra.com/cgi-bin/upload-illustration.mpl> 
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