Question 1103434
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in how many ways can five couples be seated in a row if


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a.  there are no restrictions?                             10! = 10*9*8*7*6*5*4*3*2*1 = 3628800 ways.


b.  each couple must be seated together?                   {{{5!*2^5}}} = 120*32 = 3840 ways  (120 permutations for 5 objects, each of which can be in one 
                                                          of the two states: (h,w)  or (w,h),  where "h" stands for husband and "w" stands for wife.


c.  each husband must be seated to the left of his wife?   5! = 5*4*3*2*1 = 120 ways.
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