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Difficulty: MediumAnalogy and Classification

During a data encryption analysis, a student is asked to classify four specific data blocks represented by four-letter strings. Three of these strings are generated using the identical sequential shifting rule based on the standard 26-letter English alphabet. Which of the following data blocks fails to follow the established encryption rule?

  1. A
    HKPN
  2. B
    CFUS
  3. RUFHAnswer
  4. D
    MPKI

Answer

The correct answer is the string RUFH.
The string RUFH is the correct answer because it deviates from the common pattern shared by the other three strings. While it correctly follows the first two steps of the pattern (a forward shift of 3, followed by its alphabetical opposite), the final step deviates. The established pattern requires a backward shift of 2 positions (-2), which from F (6) would yield D (4). However, RUFH ends with an H (8), representing an incorrect +2 shift.

Step-by-Step Solution

1
Analyze the alphabetical position of the letters in the first group to identify a potential structural pattern.
In the string HKPN: H (8) to K (11) is a +3 shift. K (11) and P (16) form a reverse alphabetical pair (sum = 27). P (16) to N (14) is a -2 shift.
Determining the step-by-step mathematical shifts establishes the baseline logical rule for classification.
2
Apply this hypothesized rule (+3, reverse pair, -2) to the other options to verify consistency.
CFUS: C(3)+3=F(6); F(6)+U(21)=27; U(21)-2=S(19). Valid. MPKI: M(13)+3=P(16); P(16)+K(11)=27; K(11)-2=I(9). Valid.
Checking multiple strings confirms the structural rule is universally applied across the legitimate group members.
3
Evaluate the remaining string to confirm its deviation from the established pattern.
In RUFH: R(18)+3=U(21). U(21)+F(6)=27 (reverse pair). However, the final step is F(6) to H(8), which is a +2 shift instead of the expected -2 shift. The correct final letter should have been D (6 - 2 = 4).
Classification requires finding the single option that deviates from the common pattern shared by all others.

Key Concept

Letter cluster classification through sequential positional transformations and mirror pairs.
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Topics

Analogy and Classification

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