Quantitative Aptitude
Probability
1,860 Questions
Probability Questions
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$\dfrac{1}{4}$
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$\dfrac{1}{3}$
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$\dfrac{5}{6}$
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None of these
A
Correct answer
Explanation
When tossing two unbiased coins, there are 4 equally likely outcomes: HH, HT, TH, and TT. Only one of these outcomes (HH) represents getting two heads, so the probability is 1/4.
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$\dfrac{1}{2}$
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$\dfrac{5}{6}$
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$\dfrac{1}{6}$
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$\dfrac{1}{3}$
A
Correct answer
Explanation
A standard die has six faces numbered 1 through 6. The prime numbers in this set are 2, 3, and 5, totaling 3 prime numbers. The probability is 3/6, which simplifies to 1/2.
D
Correct answer
Explanation
A deck has 52 cards. There is only one ace of hearts. The number of cards that are not the ace of hearts is 52 - 1 = 51.
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$\dfrac{1}{2}$
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$\dfrac{5}{6}$
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$\dfrac{25}{52}$
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None of these
A
Correct answer
Explanation
There are 26 black cards (13 spades, 13 clubs) in a 52-card deck. Probability = 26 / 52 = 1/2.
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$\dfrac{1}{26}$
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$\dfrac{3}{52}$
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$\dfrac{4}{13}$
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None of these
A
Correct answer
Explanation
There are 52 cards. There are 2 red kings (King of Hearts and King of Diamonds). Probability = 2/52 = 1/26.
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$\dfrac{4}{13}$
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$\dfrac{5}{26}$
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$\dfrac{7}{13}$
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None of these
A
Correct answer
Explanation
There are 13 spades and 4 aces. One ace is a spade, so there are 13 + 3 = 16 favorable cards. Probability = 16/52 = 4/13.
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$\dfrac {15}{26}$
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$\dfrac {11}{26}$
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$\dfrac {1}{2}$
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$\dfrac {17}{26}$
B
Correct answer
Explanation
A standard deck has 52 cards. There are 26 black cards, 4 kings, and 4 queens. Since the 2 black kings and 2 black queens are already counted in the 26 black cards, we subtract the 26 black cards, the 2 red kings, and the 2 red queens, totaling 30 cards to exclude. This leaves 22 cards, and 22/52 simplifies to 11/26.
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$\displaystyle \dfrac{5}{6}$
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$\displaystyle \dfrac{1}{6}$
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$\displaystyle \dfrac{2}{6}$
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None of these
A
Correct answer
Explanation
A die has 6 faces. The probability of getting 3 is 1/6. The probability of getting a number other than 3 is 1 - 1/6 = 5/6.
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$\displaystyle \frac{7}{20}$
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$\displaystyle \frac{1}{4}$
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$\displaystyle \frac{2}{5}$
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$\displaystyle \frac{2}{6}$
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$\displaystyle \frac{14}{15}$
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$\displaystyle \frac{11}{15}$
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$\displaystyle \frac{7}{15}$
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$\displaystyle \frac{4}{15}$
C
Correct answer
Explanation
Total balls = 15. Ways to pick 2 balls = 15C2 = 105. Ways to pick 2 red = 8C2 = 28. Ways to pick 2 black = 7C2 = 21. Total favorable ways = 28 + 21 = 49. Probability = 49/105 = 7/15.
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$\displaystyle \frac{1}{2}$
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$\displaystyle \frac{1}{4}$
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$\displaystyle \frac{1}{3}$
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$\displaystyle \frac{1}{5}$
C
Correct answer
Explanation
Let D be Diana's age and J be Jim's age. 3D = 2J + 17. D + J = (3J) - 13. From the second eq: D = 2J - 13. Substitute into the first: 3(2J - 13) = 2J + 17 => 6J - 39 = 2J + 17 => 4J = 56 => J = 14. Then D = 2(14) - 13 = 15. Ages are 15 and 14.
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$\displaystyle \frac{4}{19}$
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$\displaystyle \frac{5}{19}$
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$\displaystyle \frac{6}{19}$
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$\displaystyle \frac{7}{19}$
C
Correct answer
Explanation
The numbers divisible by 3 between 1 and 19 are 3, 6, 9, 12, 15, and 18. There are 6 such numbers, so the probability is 6/19.
B
Correct answer
Explanation
A standard dice has faces 1, 2, 3, 4, 5, 6. All these numbers are less than 7. Thus, the probability is 6/6 = 1.
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$ \displaystyle \frac{5}{12} $
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$ \displaystyle \frac{3}{13} $
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$ \displaystyle \frac{2}{11} $
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$ \displaystyle \frac{6}{13} $
D
Correct answer
Explanation
Total cards = 52. Red cards = 26. Queens = 4. Red Queens = 2. Cards that are red or a queen = 26 + 4 - 2 = 28. Cards that are neither = 52 - 28 = 24. Probability = 24/52 = 6/13.
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$ \displaystyle \frac{1}{2} $
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$ \displaystyle \frac{2}{5} $
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$ \displaystyle \frac{3}{5} $
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0
B
Correct answer
Explanation
The recorded number of tails is 10 out of 25 tosses. The experimental probability of not getting a head is therefore 10/25 = 2/5.