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    Which of the following numbers will replace the question mark (?) in the given series? 18, 71, 21, 76, 24, 81, 27, 86, 30, ?
    Question

    Which of the following numbers will replace the question mark (?) in the given series?
    18, 71, 21, 76, 24, 81, 27, 86, 30, ?

    A.

    80

    B.

    82

    C.

    91

    D.

    83

    Correct option is C

    Given: 18, 71, 21, 76, 24, 81, 27, 86, 30, ?
    Logic: 
    Odd positions:  increasing by 3 each time.
    Even positions: increasing by 5 each time.
    Odd positions (starting with 18):
    18 + 3 = 21
    21 + 3 = 24
    24 + 3 = 27
    27 + 3 = 30
    Even positions (starting with 71):
    71 + 5 = 76
    76 + 5 = 81
    81 + 5 = 86
    86 + 5 = 91
    So, the missing number is 91.
    Thus, correct option is (c).

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