RRB NTPC · Question 13
A number series is given below with one number missing, shown by a "?". Choose from the options the correct alternative that will fit the pattern of the series. 2, 6, 12, ?, 30, 42, 56
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Answer: (A) 20
Explanation
The terms are n(n + 1): 1×2, 2×3, 3×4, 4×5 = 20, 5×6 = 30, 6×7 = 42, 7×8 = 56.