Probability Questions and Answers updated daily – Aptitude



12 Probability Questions and answers section with explanation for various online exam preparation, various interviews, Aptitude Probability online test. Probability Questions with detailed description, explanation will help you to master the topic.

Probability Questions

1. Bag contain 10 back and 20 white balls, One ball is drawn at random. What is the probability that ball is white



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Correct Ans:2/3
Explanation:
Explanation:
Total cases = 10 + 20 = 30
Favourable cases = 20

So probability = 20/30 = 2/3


2. From a pack of 52 cards, two cards are drawn together, what is the probability that both the cards are kings



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Correct Ans:1/221
Explanation:


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



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Correct Ans:35%
Explanation:
Let A = Event that A speaks the truth
B = Event that B speaks the truth

Then P(A) = 75/100 = 3/4
P(B) = 80/100 = 4/5

P(A-lie) = 1-3/4 = 1/4
P(B-lie) = 1-4/5 = 1/5

Now
A and B contradict each other =
[A lies and B true] or [B true and B lies]
= P(A).P(B-lie) + P(A-lie).P(B)
[Please note that we are adding at the place of OR]
= (3/5*1/5) + (1/4*4/5) = 7/20
= (7/20 * 100) % = 35%


4. From a pack of 52 cards, 1 card is drawn at random. Find the probability of a face card drawn.



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Correct Ans:4/13
Explanation:
Total number of cases = 52
Total face cards = 16 [favourable cases]

So probability = 16/52 = 4/13


5. A card is drawn from a pack of 52 cards. The probability of getting a queen of club or a king of heart is



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Correct Ans:1/26
Explanation:
Total number of cases = 52
Favourable cases = 2

Probability = 2/56 = 1/26


6.  In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither blue nor green?



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Correct Ans:8/21
Explanation:
Total number of balls = (8 + 7 + 6) = 21
Let E = event that the ball drawn is neither blue nor green =e vent that the ball drawn is red.
Therefore, n(E) = 8.
P(E) = 8/21.


7. Two dice are thrown simultaneously. What is the probability of getting two numbers whose product is even ?



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Correct Ans:3/4
Explanation:
Total number of cases = 6*6 = 36

Favourable cases = [(1,2),(1,4),(1,6),(2,1),(2,2),(2,3),(2,4),(2,5),(2,6),(3,2),(3,4),(3,6),(4,1),(4,2),(4,3),(4,4),(4,5),(4,6),(5,2),(5,4),(5,6),(6,1),(6,2),(6,3),(6,4),(6,5),(6,6)] = 27

So Probability = 27/36 = 3/4


8. What is the probability of getting a sum 9 from two throws of dice.



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Correct Ans:1/9
Explanation:
Total number of cases = 6*6 = 36

Favoured cases = [(3,6), (4,5), (6,3), (5,4)] = 4

So probability = 4/36 = 1/9


9. In a throw of dice what is the probability of getting number greater than 5



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Correct Ans:1/6
Explanation:
Number greater than 5 is 6, so only 1 number
Total cases of dice = [1,2,3,4,5,6]

So probability = 1/6


10. Three unbiased coins are tossed, what is the probability of getting at least 2 tails ?



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Correct Ans:1/2
Explanation:
Total cases are = 2*2*2 = 8, which are as follows
[TTT, HHH, TTH, THT, HTT, THH, HTH, HHT]

Favoured cases are = [TTH, THT, HTT, TTT] = 4

So required probability = 4/8 = 1/2


11. In a throw of coin what is the probability of getting tails.



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Correct Ans:1/2
Explanation:
Total cases = [H,T] - 2
Favourable cases = [T] -1
So probability of getting tails = 1/2


12. In a throw of coin what is the probability of getting head.



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Correct Ans:1/2
Explanation:
Total cases = [H,T] - 2
Favourable cases = [H] -1
So probability of getting head = 1/2



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