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Top Probability Aptitude Questions & Answers [2025]

Top Probability Aptitude Questions & Answers [2025]

Q: 1. What are the real-life uses of probability?

Probability is the study of events that may or may not occur. Most of the time, we use it without even realising it. In everyday life, we don't solve actual probability issues. Instead, we use subjective probability to decide on a course of action or make any decision. To forecast the weather, meteorologists employ a specialised instrument and approach. They examine every other historical database of days with identical temperature, moisture, pressure parameters, etc. Many political analysts employ probability-based strategies to forecast election results. Probability aids in the evaluation of the appropriate insurance plan for you and your family. One of the most fascinating instances of probability is winning or losing a lottery.

Q: 2. What is an aptitude test?

An aptitude test can be defined as a test that determines a person's ability or proclivity to excel in a certain activity. According to aptitude tests, individuals are said to have intrinsic talents and limitations and a natural inclination toward success or failure in different areas based on their innate qualities. Most individuals take an aptitude test to see what sorts of jobs are suitable for their abilities and interests. High school students usually take an aptitude test to decide what college degree to pursue or which college is the best option for them. The human resources departments of some firms also employ career evaluation exams to learn about a candidate's skills and shortcomings.

Q: 3. How does the medical field make use of probability?

Part of medical decision-making is based on the probability of sickness. Current management recommendations for common illnesses are increasingly based on scores that employ artificial probability criteria. Doctors employ statistics and probability in a variety of situations. Probability aids them in communicating risk levels to patients. It assists them in gaining access to clinical recommendations and evidence summaries, evaluating medical marketing and promotional materials, interpreting screening test findings, and doing research. Probability theory is used to explore the relationship between exposures and the likelihood of negative health effects in epidemiology.

Q: 4. What are some good probability questions?

Some common probability aptitude questions asked in exams include:What is the probability of getting a sum of 7 when rolling two dice?If a bag contains 3 red balls and 5 blue balls, what is the probability of picking a red ball?A coin is tossed twice. What is the probability of getting at least one head?A deck of 52 cards is shuffled. What is the probability of drawing a face card?Practicing these probability questions and answers will improve your problem-solving ability.

Q: 5. What are 100 probability examples?

Probability problems vary from basic to advanced. Some examples include:Probability of selecting a prime number from 1 to 50.Drawing a King from a shuffled deck of cards.Tossing a fair die and getting an even number.Choosing a vowel from the English alphabet.Probability of a randomly chosen student having a birthday in January.For a detailed list, refer to probability problem sets and aptitude questions on probability available in competitive exam guides.

Q: 6. What are 5 examples of probability in real life?

Weather Forecasting: Meteorologists predict the chance of rain using probability.Insurance Policies: Companies use probability to assess risks and determine premiums.Lottery and Gambling: The odds of winning are calculated using probability.Medical Testing: The likelihood of a person having a disease given a positive test result.Traffic Signals: Traffic control systems estimate congestion and optimize signals using probability models.

Q: 7. How to answer questions on probability?

To effectively solve aptitude questions on probability, follow these steps:Identify the total number of possible outcomes.Determine the favorable outcomes for the event.Apply the probability formula: P(E) = Favorable Outcomes / Total Outcomes.Use probability rules (addition, multiplication, and complementary probability) as needed.Practice different types of probability aptitude problems to improve accuracy.

Q: 8. What type of questions are asked in aptitude tests?

Aptitude tests typically cover various topics, including:Quantitative Aptitude: Number series, percentages, probability, and ratios.Logical Reasoning: Puzzles, seating arrangements, and coding-decoding.Verbal Ability: Sentence correction, reading comprehension, and synonyms.Data Interpretation: Graphs, charts, and tables.

Q: 9. What is the aptitude test for freshers?

An aptitude test for freshers is an assessment used by companies and institutions to evaluate candidates' problem-solving, analytical, and reasoning skills. It includes sections like:Numerical Ability (including probability aptitude questions)Logical and Analytical ReasoningVerbal and Communication SkillsBasic Programming (for IT roles)

Q: 10. What are the key topics in probability aptitude questions for exams?

Probability questions in aptitude tests typically cover:Basic Probability Rules (Addition & Multiplication rules)Independent & Dependent EventsConditional ProbabilityPermutations and Combinations in ProbabilityBayes’ TheoremPracticing probability aptitude questions regularly will improve your problem-solving skills and help you ace competitive exams.

By Nitin Gurmukhani

Updated on Mar 01, 2025 | 6 min read | 13.8k views

Probability is a fundamental concept in mathematics that measures the likelihood of an event occurring. Whether expressed as a percentage (0% to 100%) or a fraction (0 to 1), probability plays a crucial role in decision-making, predictions, and data analysis.

In competitive exams, probability aptitude questions are a common topic, testing a candidate's ability to apply probability concepts to real-world scenarios. Mastering probability can help improve problem-solving skills, making it easier to tackle quantitative sections in exams like CAT, GRE, GMAT, and banking tests.

Here are basic formulas and concepts that help compute the probability of an event:

Probability Range	0 = P(A) = 1
Rule of Complementary Events	P(AC) + P(A) = 1
Rule of Addition	(A or B) = P(A) + P(B) – P(AnB)
Disjoint Events	P(AnB) = 0
Conditional Probability	P(A \| B) = P(AnB) / P(B)
Bayes Formula	P(A \| B) = P(B \| A) × P(A) / P(B)
Independent Events	P(AnB) = P(A) × P(B)
Cumulative Distribution Function	FX(x) = P(X = x)

We also use concepts of permutations and combinations to find the probability of an event.

Checkout: Guesstimate Interview Questions & Answers

Now, let’s look at some example probability aptitude questions and answers so you know how different types of questions in probability are approached.

Probability Aptitude Questions and Answers

Question 1: Two brothers X and Y appeared for an exam. Let A be the event that X is selected and B is the event that Y is selected.

The probability of A is 1/8 and that of B is 1/7. Find the probability that both of them are selected.

A) 1/63

B) 2/65

C) 1/56

D) 9/76

Solution:

Option C (1/56) is the right answer.

Given, A is the event that X is selected and B is the event that Y is selected.

P(A)=1/8, P(B)=1/7

If C be the event that both are selected, then

P(C)=P(A)×P(B) {A and B are independent events}

= (1/8)×(1/7)

= 1/56

Question 2: A person begins with 128 rupees and makes 6 bets, winning three times and losing three times, in random order. Both chances of winning and losing are equal. If each wager is for half the money remaining at the time of the bet, then the final result is:

A) gain of Rs 54

B) a loss of Rs 74

C) neither gain nor a loss

D) a gain or a loss depending upon the order in which the wins and losses occur

Solution:

Option B is the right answer.

Each win implies multiplying the amount by 1.5 and loss implies multiplying the amount by 0.5. Therefore, we will multiple 1.5 three times with the initial amount as well as multiply 0.5 three times.

The resultant amount in each case will be:

⇒ 128(1.5)(1.5)(1.5)(0.5)(0.5)(0.5)= Rs 54

Hence the final result is:

⇒ 128 − 54 = 74

I.e., a loss of Rs 74

Question 3: A box contains 2 blue, 3 red, and 2 green balls. If a ball is drawn randomly, what is the probability that none of the balls is green?

A) 10/12

B) 10/21

C) 10/13

D) 10/31

Solution:

Option B is the right answer.

Number of balls in the box = (2+3+2) = 7

If S is the sample space.

Then, n(S) is the total number of ways you can draw 2 balls out of 7

⇒ 7C2 = (7×6)/(2×1) = 21

Let E be the event of drawing 2 balls out of the box, which isn’t green.

⇒ n(E) = number of ways you can draw 2 balls out of the remaining (2+3) balls in the box

= 5C2

⇒ (5×4)/2 = 10

Therefore, P(E) = n(E)/n(S) = 10/21

Question 4: If a bag contains 23 toys having numbers 1 to 23 and two toys are drawn at random one after another (without replacement of the first toy), what is the probability that both toys will have even numbers?

A) 5/21

B) 9/42

C) 11/42

D) 5/23

Solution:

Option D is the right answer.

There are 11 even numbers between 1 and 23. Therefore, the probability that the first toy shows have an even number is

= 11/23

Since the first toy is not replaced, there are 10 even number of toys left in the bag is a total of 22 toys.

Hence, the probability that the second toy is numbered even is,

= 10/22

Resultant probability =11/23)×(10/22)

=5/23

Question 5: X speaks the truth in 75% of cases and Y speaks the truth in 80% of cases. What is the percentage of cases that are likely to contradict each other while narrating the same event?

A) 45%

B) 5%

C) 35%

D) 22.5%

Solution:

Option C is the right answer.

There can be two cases of X and Y contradicting each other,

Case I: X speaks the truth and Y does not.

Case II: X does not speak the truth and Y speaks the truth.

⇒ (3/4×1/5) + (1/4×4/5) = 3/20 + 4/20 = 7/20

Therefore, the percentage is 35%.

Question 6: Given a set of numbers {1, 2, 3, …., 125}. If a number is chosen at random from the above set, what is the probability that the chosen number will be a perfect cube?

A) 1/2

B) 1/25

C) 4/13

D) 1/10

Solution:

Option B is the right answer.

There are five perfect cubes between 1 and 100 ⇒ 1, 8, 27, 64 and 125.

Therefore, the probability of picking a perfect cube from the given sample space is

= 5/125

= 1/25

Also Read: Interview Tips to Stand out

Conclusion

Acing a probability aptitude question requires consistent practice and a clear understanding of fundamental probability concepts. By mastering the basic formulas and solving diverse problems, you can confidently tackle probability-based questions in competitive exams. Remember, the key to success is continuous learning and application.

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