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    Question

    What will come in place of the question mark (?) in the

    following series? 121, 115, 102, 82, 55, ?
    A 21 Correct Answer Incorrect Answer
    B 31 Correct Answer Incorrect Answer
    C 18 Correct Answer Incorrect Answer
    D 41 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Check differences:

    121 - 115 = 6

    115 - 102 = 13

    102 - 82 = 20

    82 - 55 = 27

    Clearly, difference increases by 7 each time:

    6, 13, 20, 27 → next is 34

    So, 55 - 34 = 21

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