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Aptitude miscellaneous
  1. In a ward-robe, Nitish has 3 trousers. One of them is black, second is blue and third brown. In this ward-robe, he has 4 shirts also. One of them is black and the other 3 are white. He opens his ward-robe in the dark and picks out one shirt-trouser pair without examining the colour. What is the likelihood that neither the shirts nor the trousers are black ?










  1. View Hint View Answer Discuss in Forum

    Probability that trousers are not black = 2/3
    Probability that shirts are not black = 3/4

    Correct Option: D

    Probability that trousers are not black = 2/3
    Probability that shirts are not black = 3/4
    Required robability = 2/3 x 3/4 = 1/2

  1. Murari has 9 pair of dark blue socks and 9 pair of black socks. He keeps them all in the same bag. If he picks out three socks at random What is the probability that he will get a matching pair?










  1. View Hint View Answer Discuss in Forum

    Since, there are only two types of socks in the bag. so, if murari pick up 3 socks then certainly two of them are of same type. Thus this is a certain event.

    Correct Option: C

    Since, there are only two types of socks in the bag. so, if murari pick up 3 socks then certainly two of them are of same type. Thus this is a certain event.
    Hence required probability = 1

  1. An anti-aircraft gun can take a maximum of four shots at an enemy plane moving away from it ,The probability of hitting the plane at the first, second, third and fourth shots are 0.4, 0.3, 0.2, and 0.1 respectively. What is the probability that the plane is hit when all the four shots are fired?










  1. View Hint View Answer Discuss in Forum

    First we find the probability that the plane is not hit
    = (1 - 0.4) ( 1 - 0.3) (1 - 0.2) (1 - 0.1)
    = 0.6 x 0.7 x 0.8 x 0.9 = 0.3024

    Correct Option: C

    First we find the probability that the plane is not hit
    = (1 - 0.4) ( 1 - 0.3) (1 - 0.2) (1 - 0.1)
    = 0.6 x 0.7 x 0.8 x 0.9 = 0.3024

    ∴ probability that the plane is hit = 1 - 0.3024
    = 0.6976

  1. Four boys and three girl stand in queue for an interview. The probability that they stand in alternate position is










  1. View Hint View Answer Discuss in Forum

    Total number of possible arrangement for 4 boy and 3 girls in a queue = 7!
    when they occupy alternate position then the arrangement would be like
    BGBGBGB. Thus the total number of possible arrangement = 4! x 3!

    Correct Option: B

    Total number of possible arrangement for 4 boy and 3 girls in a queue = 7!
    when they occupy alternate position then the arrangement would be like
    BGBGBGB. Thus the total number of possible arrangement = 4! x 3!
    ∴ Required probability = 4! x 3! / 7!
    = (4 x 3 x 2 x 3 x 2) / (7 x 6 x 5 x 4 x 3 x 2) = 1/35

  1. An elevator starts with 5 passengers and stops at 8 different floors if the house. Find out the probability of all the 5 passengers alighting at different floors.










  1. View Hint View Answer Discuss in Forum

    Required probability = favorable number of cases/ total number of
    =8P5 / 8 5 = 105/512

    Correct Option: B

    Required probability = favorable number of cases/ total number of
    =8P5 / 8 5 = 105/512