Probability
- Out of 13 applicants for a job, there are 5 women and 8 men It is desired to select 2 persons for the job, The probability that atleast one of the selected persons will be a woman, is
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Total ways = 13c2
Favourable number ways of selecting men only = 8c2
∴ Probability of selecting no woman
= 8c2 / 13c2
= 14/39Correct Option: A
Total ways = 13c2
Favourable number ways of selecting men only = 8c2
∴ Probability of selecting no woman
= 8c2 / 13c2
= 14/39
∴ Probability of selecting at least one woman
= 1 - (14 / 39)
= 25 / 39
- Five coins are tossed at a time. Then, the probability of obtaining at least one tail is
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Total events = n (s) = 25 = 32
n(E) of getting heads = 1
p(E) = 1/32
∴ n(E) = 1 - p(E)Correct Option: A
Total events = n (s) = 25 = 32
n(E) of getting heads = 1
p(E) = 1/32
∴ n(E) = 1 - p(E) = 1 - 1/32 = 31/32
- A and B are two events such that P(A) = 0.3 and P ( A∪B) = 0.8. If A and B are independent, then P (B) is
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Let P(B) = x
Given, P(A∪B) = 0.8 and P(A) = 0.3
⇒ P(A) + P(B) - P(A∩B) = 0.8
⇒ P(A) + P(B) - P(A) P(B) = 0.8 {∵A and B are independent}Correct Option: E
Let P(B) = x
Given, P(A∪B) = 0.8 and P(A) = 0.3
⇒ P(A) + P(B) - P(A∩B) = 0.8
⇒ P(A) + P(B) - P(A) P(B) = 0.8 {∵A and B are independent}
⇒ 0.3 + x - 0.3x = 0.8
⇒ 0.7x = 0.5
∴ x = 5/7
- A box contains 24 marbles, some are green and other are blue. If a marble is drawn at random from the box, the porbability that it is green is 2/3. The number of blue balls in the box is
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Let the number of green marble = x
Then, Probability of getting a green marble
= xc1 / 24c1 = 2/3Correct Option: D
Let the number of green marble = x
Then, Probability of getting a green marble
= xc1 / 24c1 = 2/3
⇒ x/24 = 2/3
⇒ x = 16
- A bag contains 3 red, 4 white and 7 black balls. The probability of drawing a red or a black ball, is
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Here, total balls are 14.
∴ Required probability = (3c1 + 7c1) / 14c1Correct Option: C
Here, total balls are 14.
∴ Required probability = (3c1 + 7c1) / 14c1
= (3 + 7)/14
= 10/14
= 5/7