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15 Probability Questions and Answers
15 solved Probability questions with step-by-step explanations. Includes formulas, shortcuts, and tips for placement tests and competitive exams.
Probability measures the likelihood of an event occurring, expressed as a number between 0 (impossible) and 1 (certain). In aptitude tests, probability questions typically involve dice rolls, card draws from a standard deck of 52 cards, coin tosses, or selection from a group of items. The basic formula is P(Event) = Number of favorable outcomes ÷ Total number of possible outcomes. Key concepts include independent events (the outcome of one does not affect another), mutually exclusive events, and conditional probability. Below are solved probability questions covering these essential patterns.
A fair die is rolled once. What is the probability of getting a prime number?
A fair die is rolled once. Probability of getting a number greater than 3?
From a standard 52-card deck, what is the probability of drawing a black card?
A bag has 6 red and 5 blue balls. Probability of picking a red ball?
A fair die is rolled once. What is the probability of getting an even number?
A bag has 1 red and 5 blue balls. Probability of picking a red ball?
From a standard 52-card deck, what is the probability of drawing a Club?
A bag has 6 red and 8 blue balls. Probability of picking a red ball?
From a 52-card deck, what is the probability of drawing a face card (J, Q, or K)?
A bag has 1 red and 7 blue balls. Probability of picking a red ball?
From a standard 52-card deck, what is the probability of drawing a red card?
A bag has 5 red and 7 blue balls. Probability of picking a red ball?
From a standard 52-card deck, what is the probability of drawing a Diamond?
A bag has 3 red and 2 blue balls. Probability of picking a red ball?
A fair die is rolled once. Probability of getting a number greater than 4?
Key Takeaways
- Total outcomes for N coin tosses = 2^N. For N dice = 6^N.
- Cards: 52 total = 4 suits × 13 ranks. Know the composition of the deck.
- For 'or' events: P(A or B) = P(A) + P(B) - P(A and B).
Frequently Asked Questions
What is the basic formula for probability?
Probability = Number of favorable outcomes ÷ Total number of possible outcomes. Always express as a fraction, decimal, or percentage between 0 and 1.
What are independent and mutually exclusive events?
Independent: Outcome of one does NOT affect the other (e.g., rolling dice twice). P(A and B) = P(A) × P(B). Mutually exclusive: Events cannot occur together (e.g., getting heads and tails on one coin toss). P(A or B) = P(A) + P(B).
More Probability Practice Resources
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