7Jul, 2021
Quantitative Aptitude: Probability Questions – Set 21
  1. If coins are tossed, then find the probability of getting at least 3 tails on the face.
    8/9
    4
    1/4
    1/2
    2/5
    Option D
    Required = (5C3) + (5C4) + (5C5) = 10 + 5 + 1 = 16
    total = 2^5 = 32
    probability = 16/32 = 1/2

     

  2. A bag contains 4 red balls, 2 black balls and 5 yellow balls. 3 balls are drawn randomly, find the probability of getting all balls are of red balls.
    2/65
    1/5
    4/165
    5/8
    2/165
    Option C
    Required = 4C3 = 4
    total = 11C3 = 165
    probability = 4/165

     

  3. A box contains 4 white balls and 8 blue balls. 2 balls are drawn randomly from the box in succession without replacement. What is the probability that they are different colors ?
    6/17
    5/12
    18/25
    16/33
    1/8
    Option D
    Probability = 4/12 * 8/11 * 4/11 * 8/12 = 2 * 4/12 * 8/11 = 16/33

     

  4. If 2 cards are selected randomly from a pack of 52 card, then what is the probability that all are face cards ?
    11/221
    8/25
    4/225
    8/29
    2/441
    Option A
    Probability = (12C2) / (52C2)
    = 12 * 11 / 52 * 51 = 11/221

     

  5. Five men and 4 women sit in a row for eating food. What is the probability that they will sit in alternate position ?
    1/26
    2/85
    3/82
    1/126
    2/ 85
    Option D
    Probability = 5! * 4! / 9! = 1/126

     

  6. What is the probability that number selected from number 1, 2 , 3 … 100 is a prime number ?
    2/5
    1/4
    5/8
    1/2
    4/7
    Option B
    Probability = 25/100 = 1/4

     

  7. In how many different ways can the letters of the word “SHARE” be arranged ?
    260
    150
    160
    120
    140
    Option D
    Number of ways = 5! = 120

     

  8. One bag contains 4 blue balls and 3 green balls. Another bag contains 5 red balls and 7 blue balls. If one ball is drawn randomly from each bag then, what is the probability that both are blue balls ?
    2
    60
    1/8
    1/3
    4/17
    Option D
    Probability = (4C1) / (7C1) * (7C1) / (12C1) = 1/3

     

  9. A box contains 4 green balls , 2 white balls and 4 blue balls. If three balls are drawn together from the box, then what is the probability of selecting that these three balls are the same colors ?
    8/17
    17/18
    2/25
    1/15
    1/30
    Option D
    Probability = (4C3) / (10C3) + (4C3) / (10C3)
    = 1/30 + 1/30 = 1/15

     

  10. How many words can be formed with the help of the letters of the word “SCHOOL” in such a way that all the words start with ‘L’ ?
    40
    60
    42
    85
    70
    Option B
    Number of ways = 5!/2! = 120/2 = 60