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TNPSC: Coding-decoding — practice questions

Logical Reasoning & Mental Ability · Group 2 & 2A · தமிழ் & English

⚡ Season 1 · Group 2 & 2A
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5 questions Day 31 of the 60-day Group 2 plan

Coding-decoding is part of Logical Reasoning & Mental Ability in the TNPSC syllabus (Group 2 & 2A). The questions below are free, bilingual (தமிழ் & English) and each one has a full explanation. For a structured path, this topic is Day 31 of the free 60-day TNPSC study plan.

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Q1. In a code where each letter moves one step forward, DOG is written as EPH. How is CAT written?

A. DBUDBU B. DBTDBT C. EBUEBU D. DCUDCU
Show answer & explanation
Answer: A. DBU · DBU
Shift each letter forward by one: C to D, A to B, T to U, giving DBU.

Q2. If A = 1, B = 2, ... Z = 26, what is the sum of the letters in the word CAB?

A. 55 B. 44 C. 77 D. 66
Show answer & explanation
Answer: D. 6 · 6
C + A + B = 3 + 1 + 2 = 6.

Q3. If each letter is shifted one step forward, how is HEAD coded?

A. IFBDIFBD B. GFBEGFBE C. IFBEIFBE D. IEBEIEBE
Show answer & explanation
Answer: C. IFBE · IFBE
H to I, E to F, A to B, D to E gives IFBE.

Q4. If letters are written by their positions so that EAT becomes 5-1-20, how is TEA written?

A. 1-5-201-5-20 B. 5-20-15-20-1 C. 20-5-120-5-1 D. 20-1-520-1-5
Show answer & explanation
Answer: C. 20-5-1 · 20-5-1
T = 20, E = 5, A = 1, so TEA is 20-5-1.

Q5. If BOOK is coded by reversing its letters as KOOB, how is WORD coded?

A. DORWDORW B. RDOWRDOW C. WRODWROD D. DROWDROW
Show answer & explanation
Answer: D. DROW · DROW
Reversing the letters of WORD gives DROW.
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