Difficulty: Medium
Correct Answer: 45
Explanation:
Introduction / Context:
In many number-series questions, the guiding rule is that each term equals the sum of the two preceding terms (a Fibonacci-like construction). Detecting one violation pinpoints the wrong term.
Given Data / Assumptions:
Concept / Approach:
Test the Fibonacci-sum rule a(n) = a(n-1) + a(n-2). If the rule holds everywhere except at one index, that index is the wrong term.
Step-by-Step Solution:
Check 3rd term: 13 + 14 = 27 ✓Check 4th term: 14 + 27 = 41 ≠ 45 → mismatchAssuming the rule is correct, the 4th term should be 41, not 45.Continue with corrected term (41): 27 + 41 = 68 ✓41 + 68 = 109 ✓68 + 109 = 177 ✓
Verification / Alternative check:
With only the 4th term corrected to 41, the remainder of the sequence fits the rule perfectly. No other single change yields full consistency.
Why Other Options Are Wrong:
Common Pitfalls:
Stopping at the first mismatch and changing the preceding term. The minimal-change strategy is to change the mismatching term itself (45 → 41).
Final Answer:
45
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