# Discrete Mathematics Questions and Answers – Probability

This section focuses on "Probability" in Discrete Mathematics. These Multiple Choice Questions (MCQ) should be practiced to improve the Discrete Mathematics skills required for various interviews (campus interviews, walk-in interviews, company interviews), placements, entrance exams and other competitive examinations.

1. Probability theory was invented?

A. 1638

B. 1654

C. 1674

D. 1666

View Answer

Ans : B

Explanation: The mathematical methods of probability arose in the investigations first of Gerolamo Cardano in the 1560s (not published until 100 years later), and then in the correspondence Pierre de Fermat and Blaise Pascal (1654).

2. When we perform an experiment, then the set S of all possible outcomes is called the?

A. Random Experiment

B. Event

C. Sample Space

D. Tossing Space

View Answer

Ans : C

Explanation: Sample Space : When we perform an experiment, then the set S of all possible outcomes is called the sample space.

3. If a coin is tossed, how many possible outcomes?

A. 1

B. 2

C. 3

D. 4

View Answer

Ans : B

Explanation: If a coin is tossed, there are two possible outcomes − Heads or Tails.

4. When a dice is thrown, What is the probability of any one of the numbers?

A. (1/3)

B. (5/6)

C. (2/3)

D. (1/6)

View Answer

Ans : D

Explanation: The probability of any one of the numbers is 1/6.

5. From a deck of 52 cards, if one card is picked find the probability of an ace being drawn?

A. (1/26)

B. (1/13)

C. (3/52)

D. (1/52)

View Answer

Ans : B

Explanation: Probability of being an ace = 4/52 = 1/13.

6. From a deck of 52 cards, if one card is picked find the probability of a diamond being drawn?

A. (1/4)

B. (3/26)

C. (1/6)

D. (1/13)

View Answer

Ans : A

Explanation: Probability of being a diamond = 13/52 = 1/4

7. Discrete probability distribution depends on the properties of ___________

A. discrete variables

B. probability function

C. machine

D. data

View Answer

Ans : D

Explanation: We know that discrete probability function largely depends on the properties and types of data such as Binomial distribution can lead to model binary data such as flipping of coins.

8. A bag contains 5 red balls and some blue balls .If the probability of drawing a blue ball is double that of a red ball, then the number of blue balls in a bag is:

A. 5

B. 10

C. 15

D. 20

View Answer

Ans : B

Explanation: Let the number of blue balls be x
Then total number of balls will be 5 + x.
According to question,
x/(5 + x) = 2 X (5/5+x)
⇒ x = 10

9. Cards marked with numbers 2 to 101 are placed in a box and mixed thoroughly. One card is drawn from this box randomly, then the probability that the number on card is a perfect square.

A. (1/5)

B. (1/25)

C. (1/20)

D. (1/10)

View Answer

Ans : D

Explanation: The perfect square numbers between 2 to 101 are:
1, 4, 9, 16, 25, 36, 49, 64, 81, 100
Total numbers from 2 to 101 =100
So probability of getting a card with perfect square number is:
P (perfect square) = 10/100
⇒ P (perfect square) = 1/10

10. The annual salaries of workers in a large manufacturing factory are normally distributed with a mean of Rs. 48,000 and a standard deviation of Rs. 1500. Find the probability of workers who earn between Rs. 35,000 and Rs. 52,000.

A. 0.42

B. 0.421

C. 0.422

D. 0.423

View Answer

Ans : B

Explanation: For x = 45000, z = -2 and for x = 52000, z = 0.375. Now, area between z = -2 and z = 0.375 is equal to 0.421 or 42.1% earn between Rs. 45,000 and Rs. 52,000.

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