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  • Question
  • The number of tosses that have to be made in order that there is 99% probability of getting at least one head is?


  • Options
  • A. 5
  • B. 7
  • C. 6
  • D. 8

  • Correct Answer


  • Explanation

    Corresponding to n tosses, the Probability of getting no head = (1/2)n and,
    Therefore, the probability of getting at least one head = 1 - (1/2)n
    Now, 1 - (1/2)n ? 99/100
    ? (1/2)n ? 1/100
    ? n ? 7

  • Tags: Bank Exams, CAT, Bank Clerk, Bank PO

    Probability problems


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    • 1. 
      The probability that a marksman will hit a target is given as 1/5. Then his probability of at least one hit in 10 shots, is?

    • Options
    • A. 1 - (4/5)10
    • B. 1/ (5)10
    • C. 1 - 1/ (5)10
    • D. (4/5)10
    • Discuss
    • 2. 
      The probability that a person will hit a target in shooting practice is 0.3 . If he shoots 10 times. Then the probability of his shooting the target is?

    • Options
    • A. 1
    • B. 1 - (0.7)10
    • C. (0.7)10
    • D. (0.3)10
    • Discuss
    • 3. 
      The probability that a man lives after 10 years is 1/4 and that his wife is alive after 10 years is 1/3. The probability that neither of them is alive after 10 years is?

    • Options
    • A. 1/2
    • B. 1/12
    • C. 7/12
    • D. 3/4
    • Discuss
    • 4. 
      The chance of throwing a total of 3 or 5 or 11 with two dics is?

    • Options
    • A. 5/36
    • B. 1/9
    • C. 2/9
    • D. 19/36
    • Discuss
    • 5. 
      Seven white balls and three black balls are randomly placed in a row, The probability that no two black balls are placed adjacently equals?

    • Options
    • A. 1/2
    • B. 7/15
    • C. 2/15
    • D. 1/3
    • Discuss
    • 6. 
      If an integer is selected at random from 1 to 100. The probability that it relatively prime to 100 is?

    • Options
    • A. 2/5
    • B. 61/100
    • C. 17/100
    • D. 19/100
    • Discuss
    • 7. 
      n books are to be arranged on a self. These include m volumes of a science book (m < n). The probability that in any arrangement, the volumes of science books are in ascending order is?

    • Options
    • A. 1/ n!
    • B. 1/n-m!
    • C. 1/m!
    • D. m!/n!
    • Discuss
    • 8. 
      The probability that a man aged x years will die in a years is p. The probability that out of n men M1, M2, M3...... Mn each aged n years Mk will die and be the first to die is?

    • Options
    • A. 1/n2
    • B. 1 - (1 - p)n
    • C. 1/n2[1 - (1- p)n
    • D. 1/n[1 - (1 - p)n]
    • Discuss
    • 9. 
      If the probability of machine failing during a day is 0.95. The probability of its working for four consecutive days without failing is?

    • Options
    • A. 0.00000625
    • B. 0.0625
    • C. 0.16548375
    • D. 0.000625
    • Discuss
    • 10. 
      Seven white balls and three black ball are randomly placed in a row. The probability that no two black balls are placed adjacently equals?

    • Options
    • A. 1/2
    • B. 7/15
    • C. 2/15
    • D. 1/3
    • Discuss


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