Suppose 4 letters are taken out of 4 different envelopes. In how many ways, can they be reinserted in the envelopes so that no letter goes in to its original envelope?

A person writes letters to six friends and addresses the corresponding envelopes. In how many ways can be letters be placed in the envelopes so that all the letters are in the wrong envelopes.

A person writes letters to six friends and addresses the corresponding envelopes. In how many ways can the letters be placed in the envelopes so that all of them are in a wrong envelope

A person writes letters to six friends and addresses the corresponding envelopes. In how many ways can the letters be placed in the envelopes so that all of them are in a wrong envelope

A person writes letters to six friends and addresses the corresponding envelopes. In how many ways can the letters be placed in the envelopes so that all of them are in a wrong envelope

In how many ways we can put 5 letters into 5 corresponding envelopes so that atleast one letter go the wrong envelope?

In how many ways we can put 5 writings into 5 corresponding envelopes so that no writing go to the corresponding envelope ?