Page 102 - Mathematics Class - XI

Viva-Voce

1. What is meant by an elementary event?
Ans. Each outcome of a random experiment is known as an elementary event.

2. Two coins are tossed simultaneously. What is the probability of getting only one head?
Ans. When two coins are tossed, the possible outcomes can be {HH, HT, TH, TT}
Total no. of outcomes = 4
Favourable outcomes are HT and TH

2 1
\ P (getting only one head) = =
4 2
3. What is the probability of an impossible event?
Ans. P (an impossible event) = 0

4. What do you understand by the probability of an event?
Ans. If there are n elementary events associated with a random experiment and m of them are favourable to an
event A, then the probability of occurrence of A is defined as:
m
P (A) =
n

MCQs

1. The total number of sample space when a die is thrown 2 times.
a) 6 b) 12 c) 18 d) 36

2. The total number of sample space when a coin is tossed and a die is thrown.
a) 6 b) 12 c) 8 d) 16
3. Three identical dice are rolled. What is the probability that the same number will appear on each of them?

a) 1 b) 1 c) 1 d) 3
6 36 18 28
4. A boy contain 5 black and 5 write balls. Ram pulls out two balls what is the probability that both the balls
are of the same colour.
a) 9 b) 2 c) 3 d) 4
20 9 20 9
5. The probability of getting the number 6 at least once in a regular die if it can roll it 6 times?
1
5
a) 1 5 6 b) 1 1 6 c) 6 d) 6

6 6 6 6
Answers: 1. d) 36 2. b) 12 3. b) 1 4. d) 4 5. a) 1 5 6

36 9 6
100