Probability (Railway Maths)

Total Questions: 29

21. An urn contains 10 black and 5 white balls. Two balls are drawn from the urn one after the other without replacement. What is the probability that both drawn balls are black? [RRB NTPC 13/03/2021 (Morning)]

Correct Answer: (b) 3/7
Solution:

22. A bag contains cards numbered between 33 and 92. If one card is drawn from the bag, the probability that the number on the drawn card is a perfect square is: [RRB NTPC 01/04/2021 (Morning)]

Correct Answer: (c) 1/15
Solution:

23. Kings and Queens of black colour are taken out from a deck of 52 playing cards. A card is drawn from the remaining well-shuffled cards. Probability of getting a spade card is: [RRB NTPC 01/04/2021 (Morning)]

Correct Answer: (c) 11/48
Solution:

24. A bag contains balls numbered 1, 2, 3, ……...20. One ball is drawn from the bag at random. What is the probability that the number on the ball drawn is divisible by 3 or 5 ? [RRB NTPC 06/04/2021 (Evening) ]

Correct Answer: (c) 9/20
Solution:

25. If 10Pᵣ = 5040, Find the value of r. [RRB NTPC 24/07/2021 (Evening) ]

Correct Answer: (d) 4
Solution:

26. A bag contains 2 red , 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue? [RRB NTPC 31/07/2021 (Evening) ]

Correct Answer: (a) 10/21
Solution:

27. Out of 5 cards with numbers 1, 2, 3, 4, 5, two are picked at random one after the other. What is the probability that the number in the second card is odd? [RRB JE 29/05/2019 (Morning)]

Correct Answer: (d) 3/5
Solution:

28. What is the probability that a two-digit number chosen at random is not a prime number? [RRB JE 29/05/2019 (Afternoon)]

Correct Answer: (b) 23/30
Solution:

29. A black, a red and a green dice are thrown at the same time. What is the probability that the sum of the three numbers is ≥ 17? [RRB JE 30/05/2019 (Evening)]

Correct Answer: (c) 1/54
Solution: