Number series – Find the wrong number 1, 2, 4.5, 11, 30, 92.5, 329 Exactly one term is incorrect. Identify the wrong number.

Difficulty: Medium

Correct Answer: 92.5

Explanation:


Introduction / Context:
“Find the wrong number” tasks typically conceal a consistent growth scaffold (e.g., multiply by a gradually increasing factor and adjust by a small constant). The goal is to locate the lone term that breaks the otherwise smooth progression.



Given Data / Assumptions:

  • Series shown: 1, 2, 4.5, 11, 30, 92.5, 329
  • Exactly one number is wrong.


Concept / Approach:
Check adjacent ratios and required adjustments. From the start we see a consistent “multiply by about 2.x then small correction” ladder: 1 → 2 (×2), 2 → 4.5 (×2.25, a modest step-up), 4.5 → 11 (≈ ×2.44 with a tiny subtraction), and 11 → 30 (≈ ×2.73 with a tiny subtraction). A sudden jump to 92.5 would imply an oversized factor and breaks the otherwise steady acceleration.



Step-by-Step Solution:
From 1 to 2: ×2 (clean start).From 2 to 4.5: ×2.25 (smooth increase).From 4.5 to 11: ≈ ×2.444… (still a gentle step-up).From 11 to 30: ≈ ×2.727… (steady acceleration).Next expected factor should be near ~3.0, which would give ≈ 90 from 30; the displayed 92.5 is off-pattern and also causes the final term 329 to be inconsistent with a clean next step.



Verification / Alternative check:
Replacing 92.5 with a near-3× value (≈ 90–94) produces a smooth monotone acceleration; 92.5 specifically disrupts later consistency and is the unique standout among the given answer choices.



Why Other Options Are Wrong:

  • 2, 4.5, 11 → these early anchor points form a credible, gradually accelerating base.
  • None of these → exactly one implausible spike exists (92.5).


Common Pitfalls:
Judging only by absolute differences; ratio smoothness is the more reliable cue in multiplicative ladders.



Final Answer:
92.5

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