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    Which of the following numbers will replace the question mark (?) in the given series?6, 3, 13, 7, 20, 11, 27, 15, 34, (?)
    Question

    Which of the following numbers will replace the question mark (?) in the given series?
    6, 3, 13, 7, 20, 11, 27, 15, 34, (?)

    A.

    19

    B.

    18

    C.

    20

    D.

    17

    Correct option is A

    Given: 6, 3, 13, 7, 20, 11, 27, 15, 34, (?)​
    Logic: Add 7 and 4 alternately to the numbers given in the series to get the alternate numbers.
    6 + 7 = 13; 13 + 7 = 20; 20 + 7 = 27; 27 + 7 = 34
    3 + 4 = 7; 7 + 4 = 11; 11 + 4 = 15
    Similarly, 15 + 4 = 19
    Thus, the correct answer is (a).​​

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