Probability Quiz Set 011 | Maths Aptitude Quiz Questions and Mock Test on Probability Set 11 | mock tests for Bank PO, SSC Exams, SO Clerical Exam, GATE Exam, LIC AO, GIC AO, etc.

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Question 1

75 defective pens are accidentally mixed with 36 good ones. It is not possible to just look at a pen and tell whether it is defective or not. One pen is taken out at random. What is the probability that it is a defective pen?

${25/37}$.

$77/111$.

$26/111$.

$30/111$.

Soln.
Ans: a

Out of the total number of pens = 111, the chances favoring defective pen are 75. So the probability is 75/111 = ${25/37}$.

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Question 2

11 bowls are lying inverted on a table. 6 of them contain coins, but 5 of them are empty. What is the probability of getting a coin if one of the bowls is opened randomly?

${6/11}$.

$7/11$.

$8/11$.

$11/11$.

Soln.
Ans: a

Chances favoring a coin are 6, whereas the total chances are 11. The probability is 6/11 = ${6/11}$.

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Question 3

Two players, A and B, play a game. It is known that probability of A's victory is 0.39. What is the probability of B's victory?

0.61.

0.39.

0.5.

0.25.

Soln.
Ans: a

One of the two is going to win. Probability of A's defeat is 1 - 0.39 = 0.61, which is the probability of B's victory.

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Question 4

Two friends were born on non-leap years. What is the chance that their birthdays do not fall on the same day and month of the year?

${364/365}$.

$21/365$.

$365/365$.

$369/365$.

Soln.
Ans: a

The birthday of second friend has 365 outcomes. If it is not to match the birthday of the first friend, the number of favorable outcomes is 365 - 1 = 364. So probability is 364/365.

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Question 5

A box contains 3 maroon, 6 green and 2 khaki marbles. What is the probability of drawing a khaki marble if 2 marbles are drawn out randomly?

${19/55}$.

$2/11$.

$20/55$.

$24/55$.

Soln.
Ans: a

Total number of marbles is 11. Combinations of 2 marbles that are possible = ¹¹C₂ = ${11 × 10}/2$ = 55. If one of the two balls is khaki, then both balls will be khaki in ²C₂ = ${2 × (2 - 1)}/2$ = 1 ways. The number of ways in which non-khaki can be drawn out are 2 × (3 + 6). So total favorable outcomes = 1 + 2 × 9 = 19, and the probability is 19/55 = ${19/55}$.

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