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Probability:
- Event: Any subset of a sample space is called an event.
- Probability of Occurrence of an Event: Let S be the sample space and let E be an event.
Then, E⊆S
∴ P(E) = n(E)′/n (S) - Sample space: When we perform an experiment, then the set S of all possible outcomes is called the Sample space.
Aptitude Questions (Probability):
1. In a simultaneous throw of two coins, the probability of getting at least one head is:
A) (1/2)
B) (1/3)
C) (2/3)
D) (3/4)
E) None of these
View Answer
Answer: option (D)
Explanation:
Here S = {HH, HT, TH, TT}
Let E = event of getting at le* one head = {HT, TH, HH}
∴ P(E) = (n(E)/n(S)) = (3/4)
2. Three unbiased coins are tossed. What is the probability of getting at least 2 heads?
A) (1/4)
B) (1/2)
C) (1/3)
D) (1/8)
E) None of these
View Answer
Answer: option (B)
Explanation:
Here S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH}
Let E = event of getting at least two heads = {THH, HTH, HHT, HHH}
∴ P(E) = (n(E)/n(S)) = (4/8) = (1/2)
3. Three unbiased coins are tossed. What is the probability of getting at most 2 heads?
A) (3/4)
B) (1/4)
C) (3/8)
D) (7/8)
E) None of these
View Answer
Answer: option (D)
Explanation:
Here S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH}
Let E = event of getting at most two heads
Then, E = {TTT, TTH, THT, HTT, THH, HTH, HHT}
∴ P(E) = (n(E)/n(S)) = (7/8)
4. In a single throw of a dice, what is the probability of getting a number greater than 4?
A) (1/2)
B) (1/3)
C) (2/3)
D) (1/4)
E) None of these
View Answer
Answer: option (B)
Explanation:
When a dice is thrown, we have S = {1, 2, 3, 4, 5, 6}
Let E = event of getting a number greater than 4 = {5, 6}
∴ P(E) = (n(E)/n(S)) = (2/6) = (1/3)
5. In a simultaneous throw of two dice, what is the probability of getting a total of 7?
A) (1/6)
B) (1/4)
C) (2/3)
D) (3/4)
E) None of these
View Answer
Answer: option (A)
Explanation:
We know that in a simultaneous throw of two dice, n(S) = 6 * 6 = 36
Let E = event of getting a total of 7 = {(1,6), (2,5), (3,4), (4,3), (5,2), (6,1)}
∴ P(E) = (n(E)/n(S)) = (6/36) = (1/6)