A clerk was asked to mail three report cards to three students. He addresses three envelopes but unfortunately paid no attention to which report card be put in which envelope. What is the probability that exactly one of the students received his or her own card?

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.

There are seven even greeting cards each of a different colour and seven envelopes of the same seven colours. Find the number of ways in which the cards can be put in the envelopes so that exactly four of the cards go into the envelopes of the right colour.

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

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 envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope.

In a class, there are 18 girls and 16 boys. The class teacher wants to choose one for class monitor. What she does she writes the name of each on a card and puts them into a basket and mixes thoroughly? A child is asked to pick up one card from the basket. What is the probability that the name written on the card is (i) the name of a girl? (ii) the name of a boy? (iii) the name of topper student of the class? (iv) not ''Shiv Kumar'' who is the son of Principal of this school?

A small pack of cards consists of 5 green cards 4 blue cards and 3 black cards. The pack is shuffled through and first three cards are turned face up. The probability that there is exactly one card of each colour is

There are 40 students in class X of a school of whom 25 are girls and 15 are boys. The class teacher has to select one student as a class representative. She writes the name of each student on a separate card, the cards being identical. Then she puts cards in a bag and stirs them thoroughly. She then draws one card from the bag. What is the probability that the name written on the card is the name of (i) a girl? (ii) a boy?

There are 40 students in Class X of a school of whom 25 are girls and 15 are boys. The class teacher has to select one student as a class representative. She writes the name of each student on a separate card, the cards being identical. Then she puts cards in a bag and stirs them thoroughly. She then draws one card from the bag. What is the probability that the name written on the card is the name of (i) a girl?(ii) a boy?

A, B, and C are independent witness of an event which is known to have occurred. A speaks the truth three times out of four B four times out of five and C five times out of six. What is the probability that the occurrence will be reported truthfully be majority of three witnesses?

A multiple choice emamination has 5 questions. Each question has three alternative answers of which exactly one is correct. The probability that a student will get 4 or more correct answers just guessing is