Three letters are dictated to three persons and an envelope is addressed to each of them the letters are inserted into the envelopes at random so that each envelop contains exactly one letter . find the probability that at least one letter is in its proper envelope.

(b)Three letters are written to different persons and addresses on the envelope are written.without looking at the addresses,the letters are put into the envelopes,the probability that letters go into right envelopes.

A word consists of 9 letters: 5 consonants and 4 vowels. Three letters are chosen at random. Find the probability that the selection of the three letters contains more than one vowel.

Arun writes letter to 3 to his friends He asks each of them to copy the letter and mail to 3 different persons with the request that they continue the chain similarly . Assuming that the chain is not broken and that it costs re.1 to mail one letter. Find the cost if all the letters in the 8 sets are considered.

A bag contains 8 red and 5 white balls.Three balls are drawn at random.Find the probability that one ball is red and two balls are white.

The letters of the word "SOCIETY" are placed at random in a row Find the number of arrangements of the letters of the given word in a row so that the three vowels come together.

Arun writes letter to 3 to his friends He asks each of them to copy the letter and mail to 3 different persons with the request that they continue the chain similarly . Assuming that the chain is not broken and that it costs re.1 to mail one letter. Find the number of letters in the 2nd and 3rd set

Suppose that the letters of the word "INSTITUTION" are arranged together at random. Find the number of arrangements of the letters so that the three T's are together.

A person writes a letter to four of his friends. He asks each one of them to copy the letter 'and mail to four different persóns with instruction that they move the chain similarly. Assuming that the chain is not broken and that it costs 50 paise to mail one letter. Find the amount spent on the postage when 8^ th set of letter is mailed.