Checkout JEE MAINS 2022 Question Paper Analysis : Checkout JEE MAINS 2022 Question Paper Analysis :

The first 12 letters of the English alphabet are to be written at random so that there are exactly 4 letters between A and B. the number of ways this can be done is?

1) 7.10!

2) 2.10!

3) 21.10!

4) 14.10!

Answer: (4) 14.10!

Solution: The number of ways arranging A and B are: A1B6 or 2&7 or 3&8 or 7&12

Number of ways of the arrangement of remaining letters in 10 places can be done in 10! ways

Therefore, total number of arrangements = 2 x 7 x 10! = 14 x 10!

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