Probability


  1. A box contains 3 white and 2 red balls. If we draw one ball and ball and without replacing the first ball. The probability of drawing red ball in the second drawn is ?









  1. View Hint View Answer Discuss in Forum

    Total balls in the box = 5
    Second red ball can be drawn in two ways
    Case I. First ball is white and second ball is red.
    Its probability = 3/5.2/4 = 6/20 = 3/10
    Case II: First ball is red and second ball is red
    Its probability = 2/5.1/4 = 2/20 = 1/10

    Correct Option: B

    Total balls in the box = 5
    Second red ball can be drawn in two ways
    Case I. First ball is white and second ball is red.
    Its probability = 3/5.2/4 = 6/20 = 3/10
    Case II: First ball is red and second ball is red
    Its probability = 2/5.1/4 = 2/20 = 1/10
    Hence, reqd. probability
    = 3/10 + 1/10 = 4/10 = 2/5


  1. Three mangoes and three apples are kept in a box. if two fruits are chosen at random. find the probability that one is a mango and the other is an apple.











  1. View Hint View Answer Discuss in Forum

    Total number of ways
    = n(s) = 6c2 = 15
    Favorable number of ways
    = n(E) = 3C1 x 3C1= 9

    Correct Option: B

    Total number of ways
    = n(s) = 6c2 = 15
    Favorable number of ways
    = n(E) = 3C1 x 3C1= 9
    ∴ Required probability = 9/15 = 3/5



  1. The probability that a man will be alive for 10 more years is 1/4 and the probability that his wife will alive for 10 more years is 1/3 .The probability that none of them will be alive for 10 more years, is











  1. View Hint View Answer Discuss in Forum

    Required probability = P(A) x P(B)
    = (1 - 1/4) x (1 - 1/3)

    Correct Option: B

    Required probability = P(A) x P(B)
    = (1 - 1/4) x (1 - 1/3) = 3/4 x 2/3 = 1/2


  1. In a lottery 10000 tickets are sold and ten prizes are awarded. What is the probability of not getting a prize, if you buy one ticket ?









  1. View Hint View Answer Discuss in Forum

    Total lottery tickets = 10000
    Total prize in the lottery = 10
    ∴ Probability getting a prize
    = 10/10000 = 1/1000

    Correct Option: C

    Total lottery tickets = 10000
    Total prize in the lottery = 10
    ∴ Probability getting a prize
    = 10/10000 = 1/1000

    Now, probability of not getting a prize
    = 1 - probability of getting a prize
    = 1 - (1/1000)
    = 999/1000



  1. Tow persons A and B appear in an interview for two vacancies. If the probabilities of their selections are 1/3 and 1/6 respectively, then the probability that none of them is selected, is











  1. View Hint View Answer Discuss in Forum

    Required probability = P (A) x p (B)
    = (1- 1/4) x (1- 1/6)

    Correct Option: A

    Required probability = P (A) x p (B)
    = (1- 1/4) x (1- 1/6) = (3/4) x (5/6)
    = 5/8