Question 992416
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There are 5 ways to select the first digit (only 5 because you cannot use zero as a first digit of a four digit number).  Then, because you have to not consider the digit selected for the first digit, but are now allowed to use zero, there are, for each of the 5 ways to select the first digit, 5 ways to select the second digit, for a total of 25 ways to select the first two digits.  Then, for each of those 25 ways to select the first two digits there are 4 ways to select the third digit.  Then there are 3 ways to select the last digit.  5 X 5 X 4 X 3.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it

*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \