We've covered this topic in our YouTube class. In this post you'll find the class recording, downloadable PDFs, and practice questions.
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Reasoning – Chapter 05: Coding Decoding
1. Core Concepts & Positional Rules
Coding involves encrypting a message based on a specific logic, while Decoding deciphering it back to its original form. Mastering letter positions and reverse pairs is mandatory for solving questions quickly.
- Golden Positional Rule: Left Position + Right Position = \(27\). To find the reverse rank: \(\text{Right Position} = 27 - \text{Left Position}\).
- EJOTY Shortcut (Multiples of 5): \(E(5) - J(10) - O(15) - T(20) - Y(25)\)
- CFILORUX Shortcut (Multiples of 3): \(C(3) - F(6) - I(9) - L(12) - O(15) - R(18) - U(21) - X(24)\)
- Opposite Pair Mnemonics: A-Z (Azad), B-Y (Boy), C-X (Crux), D-W (Dew), E-V (Evening), F-U (Full), G-T (GT Road), H-S (High School), I-R (Indian Railway), J-Q (Jungle Queen), K-P (Kanpur), L-O (LOVE), M-N (Man).
2. Primary Coding Patterns & Worked Examples
- Direct Positional Concatenation: If \(\text{TABLE} = 2012125\), each letter position is appended: \(T(20), A(1), B(2), L(12), E(5)\).
- Reverse Order Positional Coding: If \(\text{HEAD} = 4158\), letters are read right-to-left: \(D(4), A(1), E(5), H(8)\).
- Positional Sum & Scaling: If \(\text{CAB} = 13\), logic is \(\text{Sum} \times 2 + 1\): \((3 + 1 + 2) \times 2 + 1 = 13\). Thus for \(\text{JADE}\): \((10 + 1 + 4 + 5) \times 2 + 1 = 41\).
- Dual Enclosing Letter Coding: Each letter is replaced by its preceding \((-1)\) and succeeding \((+1)\) letters. Example: \(T \rightarrow S,U\), so \(\text{TIGER}\) becomes \(\text{SUHJFHDFQS}\).
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