Probability
- Two unbiased dice are thrown simultaneously. the probability of getting the sum divisible by 3, is ?
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n(S) = 6 x 6 = 36
n(E) = (1, 2) (2, 1), (1, 5) (2, 4) (3, 3) (4, 2) (5, 1) (3, 6) (4, 5) (5, 4) (6, 3) (6, 6) = 12Correct Option: B
n(S) = 6 x 6 = 36
n(E) = (1, 2) (2, 1), (1, 5) (2, 4) (3, 3) (4, 2) (5, 1) (3, 6) (4, 5) (5, 4) (6, 3) (6, 6) = 12
∴ P(E) = 12/36
- What is the possibility of getting at least 6 heads, if eight coins are tossed simultaneously ?
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Required probability = Probability of getting 2 tails + Probability of getting 1 tail + Probability of getting no tail.
Correct Option: A
Required probability = Probability of getting 2 tails + Probability of getting 1 tail + Probability of getting no tail.
= 8C2 x 1/256 + 8C1 x 1/256 + 8C0 x 1/256
= 37/256
- A and B aim a target. The Probability that A hits the target is 5/7 and B hits the target in 7/10. What is the probability that exactly one of them hits the target ?
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Required probability = P(A). P(B) + P (A ) . P(B)
Correct Option: B
Required probability = P(A). P(B) + P (A ) . P(B)
= 5/7 . 3/10 + 2/7 . 7/10
= 29/70
- A bag contains 5 white, 7 red and 8 black balls. If 4 balls are drawn one by one with replacement, what is the probability that all are white ?
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Probability that first ball drawn is white = 5C1 = 1/4
Since, balls are drawn with replacement, hence all the four events will have equal probability.Correct Option: A
Probability that first ball drawn is white = 5C1 = 1/4
Since, balls are drawn with replacement, hence all the four events will have equal probability.
Therefore, required probability = 1/4 x 1/4 x 1/4 x 1/4 = 1/256
- There are 8 blue and 4 white balls in a bag . A ball is drawn at random. Without replacing it another ball is drawn. Find the probability that both the balls drawn are blue ?
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Total number of balls in the bag = 12
Probability of drawing one blue ball in the first draw P(E1) = 8C1 / 12C1
= 8/12 = 2/3
After the first drawn of a blue ball, now there are 7 blue and 4 white ball in the bag. Total number of the balls in the bag is 11.
Probability of drawing one blue ball in the second drawn = P(E2) = 7C1 /11C1 = 7/11Correct Option: B
Total number of balls in the bag = 12
Probability of drawing one blue ball in the first draw P(E1) = 8C1 / 12C1
= 8/12 = 2/3
After the first drawn of a blue ball, now there are 7 blue and 4 white ball in the bag. Total number of the balls in the bag is 11.
Probability of drawing one blue ball in the second drawn = P(E2) = 7C1 /11C1 = 7/11
∴ Probability that both are blue P(E1 ∩ E2) = P(E1) x P(E2)
= 2/3 x 7/11 = 14 / 33