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n books are arranged on a shelf so that two particular books are not next to each other, There were 480 arrangements altogether. Then the number of books on the shelf is ________

(a) 5 

(b) 6 

(c) 10 

(d) 8

1 Answer

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Best answer

Correct option: (b) 6


Total arrangements = n!

Two particular books are together = (n-1) ! 2

Two particular books are not together = n! - 2 (n -1)!

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