Coding-Decoding Reasoning: Tricks & Solved Examples

Coding-Decoding checks one thing: can you spot a hidden rule and run it in reverse? There is nothing to mug up here — only patterns. Once you know the common types, most questions take under 30 seconds. THE FOUR COMMON TYPES 1) Letter coding — letters shift by a fixed number. If CAT becomes DBU, every letter moved +1 (C→D, A→B, T→U). So DOG → EPH. 2) Number coding — each letter is replaced by its position (A=1, B=2 … Z=26) or by a small arithmetic rule. 3) Substitution coding — words stand for other words (e.g. "sky is called water"); you answer using the substituted word. 4) Symbol / mixed coding — letters map to symbols or jumbled groups; match them position by position. THE ONE SKILL YOU MUST HAVE — ALPHABET POSITIONS Know positions both ways: A=1 … Z=26 and the reverse A=26 … Z=1. A handy aid is EJOTY → E=5, J=10, O=15, T=20, Y=25. From any of these you can count to a nearby letter in seconds. SOLVED EXAMPLES 1) FRIEND is coded GSJFOE. Each letter is +1, so WORLD → XPSME. 2) If "RED" = 27, the rule is position-sum: R(18)+E(5)+D(4)=27. So BLUE = 2+12+21+5 = 40. 3) Reverse coding: if WORK is coded DLIP, check the reverse alphabet — W↔D, O↔L, R↔I, K↔P (A=26 pattern). So the rule is "opposite letter". HOW TO ATTACK ANY QUESTION • First check the gap between original and coded letters (+1, −1, +2, or reverse?). • If letters don't shift cleanly, switch to number positions. • In "two words coded" questions, match the letter common to both words first — it reveals the rule fastest. Practise a few daily on Govt Exam Center and this becomes your quickest-scoring topic.