in how many ways can ten examination papers be arranged so that the best and worst never come together

Dear manisha mehra

total number of ways in which 10 examination papers be arranged = 10!

now total number of ways in which examination papers are arranged such that best and worst paper always come together =9!*2!

so number of ways in which they never come togerther = 10! -9!*2!

                                                                             =8*9!

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