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Question

What should come in place of the question mark '?' in the following number series?

12, 6, 0, -6, ?, -18

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is
-12

Number Series Logic

Analyze the given number series: 12, 6, 0, -6, ?, -18.

We need to identify the pattern connecting the terms.

  • Difference between the first and second term: $12 - 6 = 6$
  • Difference between the second and third term: $6 - 0 = 6$
  • Difference between the third and fourth term: $0 - (-6) = 6$

The series is decreasing by a constant value.

Finding the Missing Term

The pattern is an arithmetic progression where each term is obtained by subtracting 6 from the previous term.

Let the missing term be 'x'.

  • The fourth term is -6.
  • To find the fifth term (x), subtract 6 from the fourth term: $x = -6 - 6$
  • Calculation: $x = -12$
  • To verify, check the difference between the calculated fifth term (-12) and the sixth term (-18): $-12 - (-18) = -12 + 18 = 6$. The pattern holds true.

Therefore, the missing number in the series is -12.

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