Quantitative Aptitude: Probability Questions – Set 14

  1. There are 5 boys and 3 girls. A group of 3 members is to be made. Find the probability that either there are 2 boys and 1 girl or 2 girls and 1 boy?
    45/56
    44/54
    49/64
    52/58
    None of these
    Option A
    2 boy and 1 girl, prob. = 5C2*3C1/8C3
    2 girl and 1 boy, prob. = 5C1*3C2/8C3
    Add both the cases.

     

  2. A carton contains 8 black and 7 grey balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are alternately of different colors?
    7/10
    8/15
    9/14
    10/15
    None of these
    Option B
    When 1st is black, probability = 8/15 * 7/14
    When 1st is grey, probability = 7/15 * 8/14
    Add both cases.

     

  3. A carton contains 10 electric lights from which 2 lights are defective. Two lights are chosen at random. What is the probability that one of them is defective?
    11/43
    14/45
    16/45
    15/35
    None of these
    Option C
    Probability=2C1*8C1/10C2

     

  4. A bag contains 8 black and 7 grey balls. A ball is drawn out of it and put back in the bag. Then a ball is drawn again. What is the probability that both the balls are grey?
    49/225
    48/125
    25/95
    55/235
    None of these
    Option A

     

  5. A bag contains 8 black and 7 grey balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are alternately of different colors?
    3/14
    10/12
    8/15
    7/15
    6/15
    Option C
    When 1st is black, probability= 8/15 * 7/14
    When 1st is grey, probability = 7/15 * 8/14
    Add both cases.

     

  6. A bag 5 ruby and 8 white balls.Two draws of three balls each are made.What is the probability that the balls were ruby in the first draw and white in the second draw ?
    140/20449
    145/20445
    20550/150
    Cannot be determined
    None of these
    Option A
    5C3/13C3 *8C3/13C3

     

  7. The ratio of the number of womens to the number of mens is 5 : 2 in a class of 21 persons. A group of three students is to to be selected at random amongst them. What is the probability that the selected group of persons contain one mens and two womens?
    51/260
    45/266
    40/55
    37/255
    None of these
    Option B
    n(S) =21C3 = 1330
    n(E) =15C1 × 6C2 = 15 × 15 = 225
    Probability = 225/1330 = 45/266

     

  8. A bag contains 4 weige, 8 beige and 6 blue balls. If two balls are drawn at random, find the probability of both the balls being beige?
    15/154
    25/152
    28/253
    27/250
    None of these
    Option C
    n(S) =18C2 =153
    n(E) = 28
    P(E) = 28 /153 = 28/153

     

  9. In a shelf, there are 7 Computer, 6 Maths and 5 CA books. One book is picked up randomly. What is the probability that it is neither in Computer nor in CA ?
    1/5
    1/8
    1/3
    1/7
    None of these
    Option C
    Probability=6/18

     

  10. If two dices are thrown simultaneously, what is probability that sum of numbers appeared is less than 7?
    5/12
    7/12
    9/14
    10/15
    None of these
    Option A

     


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