Page 92 - Mathematics Class - XII

Viva-Voce

1. What is probability of an event?
Ans. If there are n elementary events associated with a random experiment and m of them are favourable to an
m
event , then probability of Event A is given by the ratio .
2. Define conditional probability. n
Ans. If two events E and F are associated with the same sample space, then the probability of happening of
event E, given that event F has already occurred and P (F) ≠ 0, is called the conditional probability of
happening of events E and F, written as P(E | F).

P (E | F) = Probability of number of events favourable to F which are aalso favourable to E
Probability of number of events favourrble to F

P(E F) ,( 0
P F )
P F ()
3. If A and B are two independent events, then what is the value of P(A ∩ B)?
Ans. If A and B are two independent events, then P(A ∩ B) = P(A).P(B)

4. If a coin is tossed four times, How many possible outcomes are there?
Ans. Number of possible outcomes = 2 .
4
i.e., (HHHH, HHHT, HHTH, HTHH, THHH, HHTT, HTTH, TTHH, THHT, THTH, HTHT, HTTT,
THTT, TTHT, TTTH, TTTT) outcomes.

MCQs

1. Two cards have been drawn from the deck of 52 cards then these two drawn cards will be Ace, its probability
will be

a) 1 b) 1 c) 1 d) 4
169 221 2652 663
2. If two dies are rolled at a time then the probability of sum of digits appeared on them is more than 7 is

a) 7 b) 7 c) 5 d) 5
36 12 12 36
3. There are 3 black and 4 white balls in a bag. The probability to fetch a white ball from the bag is
3 1
a) 4 b) c) d) None of these
7 7 7
4. A family has two children. Both of these will be boy, its probability is

a) 1 b) 1 c) 1 d) None of these
2 3 4

Answers: 1. a) 1 2. c) 5 3. a) 4 4. c) 1
169 12 7 4
90