Posted by Jen on Monday, July 21, 2008 at 6:41pm.
If n letters were put in n envelopes at random, what is the probability that eactlly n1 of them were in the correct envelopes?

Probabiltiy  drwls, Tuesday, July 22, 2008 at 6:04am
That depends upon how many letters can go into one envelope. If that number is one per envelope, then you cannot have just one in the wrong envelope. The one that is supposed to be in that envelope would also be in a wrong envelope.