Probability Quiz Set 002 | Maths Aptitude Quiz Questions and Mock Test on Probability Set 2 | mock tests for Bank PO, SSC Exams, SO Clerical Exam, GATE Exam, LIC AO, GIC AO, etc.

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Question 1

A class has 7 boys and 2 girls. What is the probability of choosing 1 boy and 2 girls?

${1/12}$.

$8/9$.

$2/12$.

$6/12$.

Soln.
Ans: a

Three students have to be picked. Total number of ways = ⁹C₃ = ${9 × 8 × 7}/{3 × 2 × 1} = $84. Number of ways of picking 1 boy and 2 girls = ⁷C₁ × ²C₂ = 7. So probability = $7/84$ = ${1/12}$.

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Question 2

A dice is thrown once. What is the probability that we get a number greater than 4?

1/3.

2/3.

5/6.

Soln.
Ans: a

Total outcomes = 6. Favorable outcomes are 2: getting a 5 or 6. The required probability is 2/6 = 1/3.

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Question 3

What is the probability of getting a head when a coin is tossed in the air?

1/2.

1/4.

Soln.
Ans: b

Total outcomes are 2, H or T. The number of favorable chances for heads is 1. So probability is 1/2.

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Question 4

A box contains 82 red balls and an unknown number of blue balls. If the probability of drawing a blue ball is 2 times the probability of drawing a red ball, then how many blue balls are there in the box?

164.

169.

159.

174.

Soln.
Ans: a

Let the number of blue balls be x. Chances of drawing a blue ball are $x/{x + 82}$ = 2 × $82/{x + 82}$, which gives x = 2 × 82 = 164.

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Question 5

A class has 5 boys and 3 girls. What is the probability of choosing 1 boy and 2 girls?

${15/56}$.

$6/8$.

$16/56$.

$20/56$.

Soln.
Ans: a

Three students have to be picked. Total number of ways = ⁸C₃ = ${8 × 7 × 6}/{3 × 2 × 1} = $56. Number of ways of picking 1 boy and 2 girls = ⁵C₁ × ³C₂ = 15. So probability = $15/56$ = ${15/56}$.

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