Question 322420
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a.  There are 26 ways to select the first letter, then 25 ways to select the 2nd letter, then 24 ways to select the 3rd letter and 23 ways to select the 4th letter.  There are 10 ways to select the first digit, 9 ways to select the second digit...and so on.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 26\ \times\ 25\ \times\ 10\ \times\ 9\ \times\ 8\ \times\ 7\ \times\ 24\ \times\ 23]


b.  Since you can repeat letters, the calculation changes to:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 26\ \times\ 26\ \times\ 10\ \times\ 9\ \times\ 8\ \times\ 7\ \times\ 26\ \times\ 26]


You get to do your own arithmetic.



John
*[tex \LARGE e^{i\pi} + 1 = 0]
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