Probability Quiz Set 016 | Maths Aptitude Quiz Questions and Mock Test on Probability Set 16 | mock tests for Bank PO, SSC Exams, SO Clerical Exam, GATE Exam, LIC AO, GIC AO, etc.

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Question 1

A box contains 41 red balls and an unknown number of blue balls. If the probability of drawing a blue ball is 3 times the probability of drawing a red ball, then how many blue balls are there in the box?

123.

128.

118.

133.

Soln.
Ans: a

Let the number of blue balls be x. Chances of drawing a blue ball are $x/{x + 41}$ = 3 × $41/{x + 41}$, which gives x = 3 × 41 = 123.

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Question 2

A bag contains 2 Red, 6 Blue and 3 Green marbles. What is the probability of drawing a Red marble if 2 marbles are drawn out randomly?

${19/55}$.

$3/11$.

$20/55$.

$24/55$.

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 red, then red + red is one possibility, and 2 × (6 + 3) are the other possibilities. So total favorable outcomes = 1 + 2 × 9 = 19, and the probability is 19/55 = ${19/55}$.

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Question 3

12 bowls are lying inverted on a table. 8 of them contain marbles, but 4 of them are empty. What is the probability of getting a marble if one of the bowls is opened randomly?

${2/3}$.

$9/12$.

$4/3$.

$7/3$.

Soln.
Ans: a

Chances favoring a marble are 8, whereas the total chances are 12. The probability is 8/12 = ${2/3}$.

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Question 4

Karmjeet and Sham are friends. What is the probability that both will have different birthdays, ignoring a leap 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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