Let f(n) denote the number of ways in which n letters go into n envelops so that no letter is in the correct envelope, (where `n>= 5`), then `f(5)/11` equals

The number of ways in which 5 letters can be placed in 5 marked envelopes, so that no letter is in the right encelope, is

If the number of ways in which 7 letters can be put in 7 envelopes such that exactly four letters are in wrong envelopes is N, then

Let N denotes the number of ways in which 3n letters can be selected from 2n A's, 2nB's and 2nC's. then,

There are 3 letters and 3 directed envelopes. Write the number of ways in which no letter is put in the correct envelope.

The number of ways in which four different letters can be put in their four addressed envelopes that

There sre three letters asnd three envelopes. Find the total number of wys in which letters can be put into the envelopes so that each envelope has only one letter.

Let N denote the number of ways in which n boys can be arranged in a line so that 3 particular boys are seperated then N is equal to

Let f(n,k) denote the number of ways in which k identical balls can be colored with n colors so that there is at least one ball of each color.Then f(2n,n) must be equal to a.^(2n)C_(n) b.^(2n-1)C_(n+1) c.^(2n-1)C_(n) d.none of these