Probability

1 Two dice are thrown simultaneously. Find the probability of obtaining a total score of seven.

(a)1/6 (b)1/36 (c)2/35 (d)1/12

2 What is the probability of getting exactly three heads while tossing 4 coins at a time?

(a)1/6 (b)1/3 (c) 1 / 4 (d)1/12

3 What is the probability of getting atleast three heads while tossing 5 coins at a time?

(a)1/6 (b)1/3 (c) 1 / 4 (d)1 / 2

4 What is the probability of getting atmost three heads while tossing 5 coins?

(a)12 /16 (b)13 / 16 (c) 12 / 32 (d)14 / 26

5 What is the probability of getting doublets while throwing 2 dice simultaneously?

(a)1/6 (b)1/3 (c) 1 / 4 (d)1 / 2

6 What is the probability that a number selected from 1, 2, 3….25 is a prime number?

(a)7/29 (b)9/25 (c)8/25 (d)1/25

7 Find the probability of getting heads in all four trials when a coin is tossed four times.

(a)1/16 (b)1/32 (c)1/64 (d)1/8

8 Two fair dice are thrown. Find the probability of getting a sum which is a prime number < 8?

(a) 11/13 (b) 13/36 (c) 1/13 (d) ¼

9 When a pair of fair dice is rolled once, what is the probability that both dice do not show up a 6?

(a) 25/36 (b) 35/36 (c) 11/36 (d) 1/6

10 An anti aircraft gun can fire four shots at a time. If the probabilities of the first, second, third and the last shot hitting the enemy aircraft are 0.7, 0.6, 0.5 and 0.4, what is the probability that four shots aimed at an enemy aircraft will bring the aircraft down?

(a) 0.036 (b) 0.934 (c) 0.964. (d) 0.042

11 A speaks truth in 75% and B in 80% of the cases. In what percentages of cases are they likely to contradict each other narrating the same incident?

(a) 25% (b) 65% (c) 35% (d) 50%

12 From a pack of 52 playing cards, four cards are drawn at random. Find the probability of drawing all the four cards of the same suit.

(a) 13C4 / 52C4

(b) 4 * (13C4 / 52C4)

(c) 4C4 / 52C4

(d) None of these

13 If two cards are drawn at random what is the probability that the 1st is a king and the 2nd belongs to heart?

a) 1/52 b) 2/13 c) 4/51 d) None of these

14 A box contains 20 electric bulbs out of which 4 are defective. Two bulbs are chosen at random from this box. The probability that at least one of these is defective is:

(a) 4 / 19 (b) 7 / 19 (c) 12 / 19 (d) 10 / 21

15 A man and his wife appear in an interview for two vacancies in the same post. The probability of husband’s selection is (1 / 7) and the probability of wife’s selection is (1 / 5). What is the probability that only one of them is selected?

(a) 4 / 5 (b) 2 / 7 (c) 8 /15 (d) 4 / 7

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