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In how many ways can 4 different letters be placed in 4 addressed envelopes (one letter in each envelope) so that no letter is placed in its own envelope?
- A9
- B8
- C12
- D6
Correct answer: A
In how many ways can 4 different letters be placed in 4 addressed envelopes (one letter in each envelope) so that no letter is placed in its own envelope?