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General Intelligence & Reasoning

Coding-Decoding Logic Patterns

High (3-5 questions in most government exams)

Concept Overview

Coding-Decoding involves encrypting letters or words based on set logic rules. Patterns include forward/backward alphabetical shifts, reverse opposite pairings, numerical positions (A=1, Z=26), and matrix-based coding.

Exam Relevance

Highly present in SSC CGL, Police SI/Constable, Railways NTPC/Group D, and Banking Assistant exams.

Key Formulas & Shortcuts

  • A-Z positions mnemonic: EJOTY (5, 10, 15, 20, 25) and CFILORUX (multiples of 3).
  • Opposite Pairs Rule: The sum of position values of opposite letter pairs is always 27 (e.g., G [7] + T [20] = 27).
  • Reverse alphabetical values: Value = 27 - forward position value.

Common Weaknesses & Mistakes

1

Failing to recall opposite pairs quickly (e.g. A-Z, B-Y, C-X, D-W).

2

Stopping after checking only the first two letters of the code; logic shifts can change halfway through the word.

3

Confusing circular alphabetical shifts (e.g., Z + 3 = C).

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