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Which number should replace the question mark? 16, 2, 15, 4, 13, 7, 10, 11, 6, ?

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posted Feb 23, 2017 by Anil Chaurasiya

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1 Answer

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Thanks for the query.

The series is comprised of two separate ones with the odd members and even members in different series.
The odd numbered members 16, 15, 13, 10, 6 is decreasing with a difference of -(d + 1), where d = 0 i.e., the common difference is -1, -2, -3 and so on.
The even numbered members 2, 4, 7, 11 are increasing with a difference of (d + 1), where d = 1 i.e., the common difference is 2, 3, 4, etc
Hence the 10th member of the series should be 11 + (4 +1) = 16

answer Feb 23, 2017 by Indranil Datta
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