CBSE Guess > Papers > Important Questions > Class XII > 2010 > Maths > Mathematics By Mr Vasu Raj

CBSE CLASS XII

Q.1. A family has two children. What is the probability that both the children are boys given that at least one of them is a boy ?

Ans. 1/3

Q. 2. Ten cards numbered 1 to 10 are placed in a box, mixed up thoroughly and then one card is drawn randomly. If it is known that the number on the drawn card is more than 3, what is the probability that it is an even number?

Ans. 4/7

Q. 3. A die is thrown three times. Events A and B are defined as below: A : 4 on the third throw B : 6 on the first and 5 on the second throw. Find the probability of A given that B has already occurred.

Ans. 1/6

Q. 4. A die is thrown twice and the sum of the numbers appearing is observed to be 6. What is the conditional probability that the number 4 has appeared at least once?

Ans. 2/5

Q. 5. Assume that each born child is equally likely to be a boy or a girl. If a family has two children, what is the conditional probability that both are girls given that
(i) the youngest is a girl,
(ii) at least one i s a girl?

Ans. 1/2, 1/3 .

Q. 6. An instructor has a question bank consisting of 300 easy True / False questions, 200 difficult True / False questions, 500 easy multiple choice questions and 400 difficult multiple choice questions. If a question is selected at random from the question bank, what is the probability that it will be an easy question given that it is a multiple choice question?

Ans. 5/9

Q. 7. Consider the experiment of throwing a die, if a multiple of 3 comes up, throw the die again and if any other number comes, toss a coin. Find the conditional probability of the event ‘the coin shows a tail’, given that ‘at least one die shows a 3’.

Ans. 0

Q. 8. Three cards are drawn successively, without replacement from a pack of 52 well shuffled cards. What is the probability that first two cards are kings and the third card drawn is an ace?

Ans. 2/5525

Q. 9. An unbiased die is thrown twice. Let the event A be ‘odd number on the first throw’ and B the event ‘odd number on the second throw’. Check the independence of the events A and B.

Ans. Independent.

Q. 10 .Prove that if E and F are independent events, then so are the events E and F′.

Paper By Mr Vasu Raj
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