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Question
In how many ways can 10 examination papers be arranged so that the best and the worst papers never come together?
Options
9 × 8!
8 × 8!
9 × 9!
8 × 9!
Solution
8 × 9!
Explanation:
Arrange 8 papers in 8! ways and two papers in 9 gaps are arranged in 9P2 ways.
Required number = 8! 9P2
= 8! × 9 × 8
= 9! × 8
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