Page 99 - Mathematics Class - XI

Viva-Voce

1. What is an outcome?
Ans. A possible result of a random experiment is called its outcome.
2. What is meant by sample space?
Ans. The set of all possible outcomes of a random experiment is called the sample space associated with the
experiment. It is denoted by the symbol S.
3. A die is thrown once. Find the probability of getting (i) an even number (ii) a prime number.
Ans. Total number of outcomes = 6
(i) Favourable outcomes are 2, 4, 6

No. of favourable outcomes 3 1
\ P (an even number) = = =
Total no. of outcomes 6 2
(ii) Favourable outcomes are 2, 3, 5

3 1
\ P (a prime number) = =
6 2
4. What is meant by an event?
Ans. A subset of the sample space associated with a random experiment is called an event.

5. What do you understand by the random experiment?
Ans. An experiment whose outcomes cannot be predicted or determined in advance is called a random
experiment.

MCQs

1. One letter is picked randomly from the word ‘PROBABILITY’. The probability of that picked letter
would be a vowel.

a) 1 b) 4 c) 2 d) 3
3 11 11 11
2. A number of four digits has been made by the digits 0, 2, 3, 5 without any repetition of digits. So, the
probability of a number which is divisible by 5 is.

a) 1 b) 4 c) 1 d) 5
5 5 30 9
3. If two dies are thrown together then what will be the probability of the sum of the digits, which have come
on the top of the dies, is more than 5.

a) 1 b) 13 c) 5 d) 5
6 18 36 18
1
5
4. Given that, P (A ∪ B) = , P (A ∩ B) = , P (B') = 1 . Then the value of P (A') will be
6 3 2
a) 1 b) 1 c) 2 d) 1
6 3 3 2
5
Answers: 1. b) 4 2. d) 3. b) 13 4. b) 1
11 9 18 3
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