Probability aptitude questions
Probability questions are part of the Quant section of placement aptitude tests. Define the equally likely sample space before counting favourable outcomes. Below are 5 worked examples with the answer and the working; practise ten fresh ones or take a timed mock when you are ready.
Example 1. One card is drawn at random from a standard pack of 52 cards. What is the probability that it is a face card?
- A. 4/17
- B. 3/13 (answer)
- C. 12/53
- D. 1/4
The pack has 12 such cards, so the probability is 12/52 = 3/13.
Example 2. Two fair dice are rolled together. What is the probability that the sum of the numbers is 5?
- A. 5/36
- B. 1/6
- C. 4/37
- D. 1/9 (answer)
Out of 36 equally likely pairs, 4 pairs add up to 5, so the probability is 4/36 = 1/9.
Example 3. A bag holds 5 red and 4 blue marbles. One marble is drawn at random. What is the probability that it is red?
- A. 5/9 (answer)
- B. 5/4
- C. 1/2
- D. 4/9
There are 5 red marbles out of 9 in total, so the probability is 5/9.
Example 4. A bag holds 3 red and 8 blue marbles. One marble is drawn at random. What is the probability that it is red?
- A. 3/11 (answer)
- B. 3/8
- C. 8/11
- D. 1/2
There are 3 red marbles out of 11 in total, so the probability is 3/11.
Example 5. A bag holds 6 red and 5 blue marbles. One marble is drawn at random. What is the probability that it is red?
- A. 5/11
- B. 6/11 (answer)
- C. 1/2
- D. 6/5
There are 6 red marbles out of 11 in total, so the probability is 6/11.
More Quant practice elsewhere: IndiaBIX, GeeksforGeeks. See the 60-day aptitude plan.