SOLUTION: Patricia owns all thirteen books in the A Series of Unfortunate Events series. In how many different orders can she place all of them on the top shelf of her bookshelf?

Any one of 13 volumes she can place to the first position;

any one of remaining 12 volumes she can place to the second position;

any one of remaining 11 volumes she can place to the third position,


   . . . . . . . . and so on . . . . . 


till the last, 13-th volume;


which gives her  13! = 13*12*11*10*9*8*7*6*5*4*3*2*1  options,  in all.


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  |  Any set of n different objects has n! different permutations.  |
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