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Home Aptitude Problems on Numbers See What Others Are Saying!
  • Question
  • The series of differences between consecutive prime numbers is represented as Cp1, Cp2, Cp3, .... Cpn , Whare Cp1 is the difference between the second and the first prime number. Find the sum of series when n = 23, given that the 23rd prime number is 83 ?


  • Options
  • A. 87
  • B. 81
  • C. 83
  • D. 85

  • Correct Answer
  • 87 

    Explanation

    Cp1 = p2 - p1 ,
    Cp2 = p3 - p2
    ..
    ..
    ..
    Cp23 = p24 - p23
    Sum of series = (p2-p1) + (p3-p2) + .....(p23-p22) + (p24-p23)
    All terms get cancelled, except p1 = 2 and p24 = 89
    So Sum = -p1 + p24
    Sum of series = -2 + 89 = 87

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

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