Number series (identify the incorrect term): 7, 8, 18, 57, 228, 1165, 6996 Exactly one term is wrong. Select the incorrect value that breaks the pattern.

Difficulty: Medium

Correct Answer: 228

Explanation:


Introduction / Context:
Some series hide a generative rule of the form “multiply by n and add n” with n increasing by 1 each step. The task is to detect the rule and identify which term violates it.



Given Data / Assumptions:

  • Sequence: 7, 8, 18, 57, 228, 1165, 6996.
  • Hypothesis: a(n+1) = a(n) * k + k with k = 1, 2, 3, 4, 5, 6, …


Concept / Approach:
Check consecutive transitions with increasing multipliers and addends: start with ×1 + 1, then ×2 + 2, ×3 + 3, etc. Any mismatch pinpoints the incorrect term.



Step-by-Step Solution:

7 → 8: 7 * 1 + 1 = 8 ✔8 → 18: 8 * 2 + 2 = 18 ✔18 → 57: 18 * 3 + 3 = 57 ✔57 → 228: Expected 57 * 4 + 4 = 228 + 4 = 232, but the term is 228 ✖If corrected to 232, then: 232 * 5 + 5 = 1165 ✔1165 * 6 + 6 = 6996 ✔


Verification / Alternative check:
After fixing the fourth transition to 232, all subsequent terms align exactly with the rule ×k + k for k = 5 and k = 6, confirming 228 is the outlier.



Why Other Options Are Wrong:

  • 8, 18, 57, 1165: Each fits the rule at its step and is therefore correct.


Common Pitfalls:
Assuming a constant multiplier or missing the incremental +k addend. Always verify every step with the presumed rule.



Final Answer:
228

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