Probability problems
- 1. A number is chosen at random among the first 120 natural numbers. The probability of the number chosen being a multiple of 5 or 15 is?
Options- A. 1/5
- B. 1/8
- C. 1/6
- D. None of these Discuss
Correct Answer: 1/5
Explanation:
? Total no. of favourable cases i,e., (5, 10, 15, 20, 25, 30, ....., 105, 110, 115, 120) = 24.
? Reqd . Prob = 24/120 = 1/5
- 2. A bag contains 7 white and 9 red balls. The probability of drawing a white ball is?
Options- A. 1/16
- B. 1/52
- C. 7/52
- D. 7/16 Discuss
Correct Answer: 7/16
Explanation:
No of white balls = 7
Red balls = 9
Total no. of balls = 7 + 9 = 16
Probability of drawing a white ball = 7/16
- 3. A card is drawn from a well shuffled pack of cards. The probability of getting a queen of club or king of heart is?
Options- A. 1/52
- B. 1/26
- C. 1/13
- D. None of these Discuss
Correct Answer: 1/26
Explanation:
Total ways = 52
There is one queen of club and one king of heart favourable ways = 1 + 1 = 2.
? Required probability = 2/52 = 1/26
- 4. Find the probability that a vowel selected at random from the 5 vowels is an 'i'.?
Options- A. 4/5
- B. 1/3
- C. 1/5
- D. 1/2 Discuss
Correct Answer: 1/5
Explanation:
Here, n(5) = {a, e, i,o, u}
and E = Event of selecting the vowel i = {i}
? P(E)= n(E)/n(S) = 1/5
- 5. If the probability that A will live 15 yr is 7/8 and that B will live 15 yr is 9/10, then what is the probability that both will live after 15 yr?
Options- A. 1/20
- B. 63/80
- C. 1/5
- D. None of these Discuss
Correct Answer: 63/80
Explanation:
Required probability = P(A) x P(B)
= (7/8) x (9/10)
= 63/80
- 6. A single letter is selected at random from the word 'PROBABILITY' . The probability that it is a vowel, is?
Options- A. 3/11
- B. 4/11
- C. 2/11
- D. 0 Discuss
Correct Answer: 4/11
Explanation:
Total number of letters = n(S) = 11
whereas, number of vowels = n(E) = 4
? Required probability = n(E)/n(s) = 4/11
- 7. The probability of drawing a red card from a deck of playing cards is
Options- A. 2/18
- B. 1/13
- C. 1/4
- D. 1/2 Discuss
Correct Answer: 1/2
Explanation:
Total number of cards n(S) = 52
Number of red cards n(E) = 26
? P(E) = n(E)/n(S) = 26/52 = 1/2
- 8. The probability of getting a composite number when a six-faced unbiased die is tossed, is
Options- A. 1/4
- B. 1/3
- C. 1/2
- D. 1 Discuss
Correct Answer: 1/3
Explanation:
n(S) = 6, n(E) = (4, 6) = 2
? P(E) = 2/6 = 1/3
- 9. When two dice are rolled, what is the probability that the sum of the numbers appeared on them is 11?
Options- A. 1/6
- B. 1/18
- C. 1/9
- D. 1 Discuss
Correct Answer: 1/18
Explanation:
n(S) = 36
n(E) = {(5,6), (6,5)} = 2
? p(E) = n(E) / n(S) = 2/36 = 1/18
- 10. Ticket numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn bears a number which is a multiple of 3 or 7?
Options- A. 1/15
- B. 1/2
- C. 2/5
- D. 7/20 Discuss
Correct Answer: 2/5
Explanation:
Clearly, n(S) = 20 and E = { 3, 6, 9, 12, 15, 18, 7, 14 } i.e., n(E) = 8
? P(E) = n(E)/ n(S) = 8/20 = 2/5
More in Aptitude:
Programming
Copyright ©CuriousTab. All rights reserved.