CODING AND DE CODING

 

📘 CODING & DECODING – Complete Notes for Competitive Exams

🔍 What is Coding-Decoding?

Coding-Decoding is a part of logical reasoning where a word or number is written in a particular code using some logic. You are required to decode the logic and apply it to find the correct answer.

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🧠 Types of Coding-Decoding Questions

1. Letter Coding

A word is coded by replacing each letter with another letter.

🔹 Example:
If BOY is coded as CPZ, how is CAT coded?

Logic:
B→C (+1), O→P (+1), Y→Z (+1)
So, C→D, A→B, T→U ⇒ DBU

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2. Number Coding

Words are coded into numbers, and you must find the pattern.

🔹 Example:
If DOG = 26, what is the code for CAT?

Logic:
D(4)+O(15)+G(7) = 26
C(3)+A(1)+T(20) = 24

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3. Symbol/Sequence Coding

Symbols or sequences are used to code the words.

🔹 Example:
If "A = +, B = -, C = *, D = /", what is the value of:
(6 C 2) A (4 D 2)?

Logic:
(6 * 2) + (4 / 2) = 12 + 2 = 14

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4. Substitution Coding

Words are replaced by other words.

🔹 Example:
If "Apple" is called "Banana", "Banana" is called "Mango", then what is the color of Banana?

If Banana = Mango, color of actual Banana is yellow, so answer is color of Mango = Yellow.

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5. Mixed Letter Coding

Statements are coded in a jumbled format.

🔹 Example:
If in a code, "Rain is beautiful" is written as ka re mo, and
"Sun is hot" is written as mo la de, then what is the code for "is"?

Answer:
Common word = "is" → common code = mo

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6. Reverse Letter Coding

Alphabets are replaced based on their reverse order.

🔹 Example:
If A = Z, B = Y, ..., M = N, then what is the code for DOG?

D(4) → W, O(15) → L, G(7) → T ⇒ WLT

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7. Clockwise/Anti-clockwise Coding

Letter positions are changed by shifting in alphabet order.

🔹 Example:
If CAT is coded as FDW, how is DOG coded?

C→F (+3), A→D (+3), T→W (+3)
So, D→G, O→R, G→J ⇒ GRJ

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🔧 Tips to Crack Coding-Decoding Questions

1. Note Alphabet Positions (A=1 to Z=26)
2. Practice Reversals (A↔Z, B↔Y…)
3. Check + or – Pattern
4. Look for Patterns in Vowels/Consonants
5. Match Word Length and Repeated Patterns
6. Avoid Guessing – Focus on Consistent Logic

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📝 Practice Questions

Q1. If PEN = 35, INK = 34, then what is the code for PAPER?

Ans: P(16)+A(1)+P(16)+E(5)+R(18) = 56

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Q2. In a certain code, ROAD = URDG, then what is the code for RAIL?

R→U (+3), O→R (+3), A→D (+3), D→G (+3) ⇒ Same logic
R→U, A→D, I→L, L→O ⇒ UDLO

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Q3. If "Blue Sky" is coded as "mo la", and "Sky High" is "la ni", then what is the code for "High"?

Common: Sky = la
"High" = ni

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🔁 Frequently Asked in:

Exam	Type	Frequency
SSC CGL/CHSL/MTS	Letter & Mixed Coding	Very High
UPSC CSAT	Logical Coding	Medium
Bank PO/Clerk	Number & Substitution Coding	High
RRB Group D/NTPC	Letter & Number Coding	High
State PSCs (APPSC, TGPSC)	Basic Logical Coding	Medium

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📚 Recommended Practice Strategy

1. Practice at least 20–30 questions daily.
2. Focus on previous year papers.
3. Make your own alphabet chart (A-Z with numbers).
4. Time yourself – aim for 20 seconds per question.

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🔢 Practice Questions (Sample 1–5):

Q1. If JRGY = ?, find the code using letter positions sum (A=1, ..., Z=26).
📝 Answer: 60

Q2. If USCD = ?, find the code using letter positions sum (A=1, ..., Z=26).
📝 Answer: 47

Q3. If OIF is coded as LRU, find the pattern used.
📝 Answer: Reverse Alphabet Code

Q4. If EXU is coded as FYV, what is the shift applied to each letter?
📝 Answer: +1

Q5. If AQC = ?, find the code using letter positions sum.
📝 Answer: 21

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🔢 Practice Questions (Q6–Q10):

Q6. If the reverse of TWCF is used and its letters are summed (A=1 to Z=26), what is the code?
📝 Answer: 52

Q7. If the reverse of KDOJNL is used and its letters are summed, what is the code?
📝 Answer: 66

Q8. If QMRP is coded as SOTR, alternating shifts were applied. Identify the two shifts used.
📝 Answer: 2, 2

Q9. If the sum of letters in AFWNJ is calculated and transformed by the formula (Sum × 2 + 3), what is the final code?
📝 Answer: 111

Q10. If the sum of letters in NTCGUY is calculated and transformed by (Sum × 2 + 3), what is the final code?
📝 Answer: 183

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🔹 Basic to Moderate Level (Q1–Q5)

Q1. If JRGY = ?, find the code using letter positions sum (A=1 to Z=26).
👉 Ans: 60

Q2. If USCD = ?, find the code using letter positions sum.
👉 Ans: 47

Q3. If OIF is coded as LRU, find the pattern used.
👉 Ans: Reverse Alphabet Code

Q4. If EXU is coded as FYV, what is the shift applied to each letter?
👉 Ans: +1

Q5. If AQC = ?, find the code using letter positions sum.
👉 Ans: 21

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🔹 Advanced Level (Q6–Q100)

Q6. If the reverse of TWCF is used and its letters are summed (A=1 to Z=26), what is the code?
👉 Ans: 52

Q7. If the reverse of KDOJNL is used and its letters are summed, what is the code?
👉 Ans: 66

Q8. If QMRP is coded as SOTR, alternating shifts were applied. Identify the two shifts used.
👉 Ans: 2, 2

Q9. If the sum of letters in AFWNJ is calculated and transformed by (Sum × 2 + 3), what is the final code?
👉 Ans: 111

Q10. If the sum of letters in NTCGUY is calculated and transformed by (Sum × 2 + 3), what is the final code?
👉 Ans: 183

Q11. If the reverse of GDTK is taken and then a +1 shift is applied, what is the resulting code?
👉 Ans: LEUH

Q12. If BRXW is coded as DSZY, what consistent shift is applied?
👉 Ans: +2

Q13. If the sum of positions of letters in LMNOP is 75, find (sum × 2 − 10).
👉 Ans: 140

Q14. If YUIR is coded using reverse alphabet and a +1 shift, what is the final code?
👉 Ans: BFWI

Q15. If PAST is written as QBTW, what is the logic?
👉 Ans: +1 shift to each letter

Q16. Reverse the word FEAR and then apply +2 shift to each letter. What is the code?
👉 Ans: TGCT

Q17. If each even-position letter in VISION is shifted +3 and odd-position letters −1, what is the result?
👉 Ans: ULUJRP

Q18. If HELLO = IGMMQ, what logic is used?
👉 Ans: +1 shift

Q19. If RANK is coded as UZQO, what shift is used?
👉 Ans: +3

Q20. If CODE = FRGH, what transformation is applied?
👉 Ans: +3 to each letter

Q21. The word MATHS is coded by reversing and applying a +2 shift. What is the final code?
👉 Ans: UJVCU

Q22. In the word STRONG, if vowels are shifted +2 and consonants −1, what is the result?
👉 Ans: RSPQMH

Q23. If SALT = UCNV, what rule is applied?
👉 Ans: +2 shift

Q24. What will be the result if reverse of FIGHT is shifted +1?
👉 Ans: UHJGF

Q25. If the sum of letters in RIVER is 69, what is (Sum ÷ 3 + 4)?
👉 Ans: 27

Q26. If LOVE is coded as MPWF, what is the code for HATE?
👉 Ans: IBUF

Q27. If alternate letters of BREAD are shifted by +1, what is the code?
👉 Ans: CSFBE

Q28. Reverse RAINS, shift vowels +2 and consonants −1. What is the code?
👉 Ans: QUGMR

Q29. If BLUE = CNVF, what logic is applied?
👉 Ans: +1 shift to each letter

Q30. If sum of letters in UNITY is 86, what is (sum ÷ 2 − 5)?
👉 Ans: 38

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Q31. ZEBRA reversed and shifted +1 = ? → BFDCS
Q32. DOG = 26, GOD = ? → 26
Q33. CAT = DBU, DOG = ? → EPH
Q34. EARTH = DUQSG (−1 shift)
Q35. CODE = DPEF (+1 shift)
Q36. MONEY = NPOFZ
Q37. SHIFT = TJIGU
Q38. BANK = CBOL
Q39. LOSE = MPVF
Q40. HURT = IVSU

Q41. PRIDE reversed = EDIRP
Q42. TABLE reversed +2 shift = VCDNG
Q43. ALPHA = BMQIB
Q44. DELTA = EFMUB
Q45. STAR = TUBS
Q46. SUN = TVO
Q47. GROW = HSQX
Q48. RISE = SJTF
Q49. JUMP = KVNQ
Q50. CODE = GRHI (Random logic)

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🔸 Complex Logic & Mixed Patterns (Q51–Q100)

Q51. Add ASCII of all letters in WATER = 87+65+84+69+82 = 387
Q52. If COLD → +2 → ENNF
Q53. HEART = JGCTV
Q54. PEACE = QFBDC
Q55. Apply −1 on even index of TRUST = TQUSU
Q56. Multiply sum of letters of LOGIC by 2 = 146
Q57. CLOCK reversed = KCOLC
Q58. SHIFT letters of NIGHT by +3 = QLJKW
Q59. Encode every second letter +3 in VALUE = VBOWF
Q60. VOTER → UPUDQ

Q61. SYSTEM → TZTUFO
Q62. NOISE → MPHRD
Q63. LAUGH → MBVHI
Q64. LAUGH = HGAUL (Reverse + alternate −1 shift)
Q65. Check if TEARS = VGCTU
Q66. Decode: ZKLO = YJKM (−1 shift)
Q67. NEAT = OFBU
Q68. BIG = DJI
Q69. DEED = FGFF
Q70. SUM = UWN

Q71. HEAT = IGCV
Q72. GREET = HTFFU
Q73. CHEER = DIFES
Q74. PARTY = QBUSZ
Q75. QUEEN = RVFFO
Q76. PEARL = QFBSM
Q77. SKILL = TLMNN
Q78. FAIL = GBJM
Q79. RATE = SBVF
Q80. RISE = TJTG

Q81. SAND = TBPE
Q82. MOON = NPPO
Q83. SUGAR = TVHBS
Q84. DEED = EFEE
Q85. BOMB = CNNC
Q86. FAITH = GBJUI
Q87. TEACH = UFBDI
Q88. STAGE = TUBHF
Q89. PRINT = QSJOU
Q90. PLANE = QMBOF

Q91. RAINY = SBJOZ
Q92. BIRDS = CJSET
Q93. ANGRY = BOHSZ
Q94. CLOUD = DMNVE
Q95. FIGHT = GJHIU
Q96. LAUGH = MBVHI
Q97. DOORS = EPPTS
Q98. WINTER = XJOUGS
Q99. SMILE = TNJMF
Q100. ROADS = SPBET

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🔴 Coding-Decoding – Advanced Difficulty (Q101–Q150)

Q101. Reverse the word 'PBZFV' and apply a +2 shift to each letter.
👉 Ans: XHBDR

Q102. Reverse the word 'HELOEO' and apply a +2 shift to each letter.
👉 Ans: QGQNGJ

Q103. If ASCII values of 'ZGFJSEW' are averaged and 5 is added, what is the resulting value?
👉 Ans: 82

Q104. If ASCII values of 'MHXIUA' are averaged and 5 is added, what is the resulting value?
👉 Ans: 81

Q105. Apply +3 to letters at odd positions and -2 to even positions in 'XBGWXLH'.
👉 Ans: AZJUAJK

Q106. Shift each letter in 'CNFLWOX' forward by its position index (1-based).
👉 Ans: DQOHZVC

Q107. Reverse 'LUNHRT' and apply a +2 shift to each character.
👉 Ans: VJTPPW

Q108. Apply +3 to odd and −2 to even positions in 'DREHLAO'.
👉 Ans: GPCJNZM

Q109. ASCII sum of 'ZAPLOQF', then divide by number of letters and add 5.
👉 Ans: 81

Q110. In 'JCKVDFH', shift letters forward by their 1-based position index.
👉 Ans: KEMZJML

Q111. Reverse 'BCRDLT' and +2 shift →
👉 Ans: VFNTEF

Q112. Shift every character in 'ZKUNGB' by its index (1-based).
👉 Ans: ALZSOH

Q113. Reverse 'PQRMNL', then apply −1 to vowels and +1 to consonants.
👉 Ans: KMLSQO

Q114. Take ASCII values of 'GLORIA', average, multiply by 2, then −10.
👉 Ans: 148

Q115. 'HYZQKL' → +3 on odd, −1 on even →
👉 Ans: KXCPNM

Q116. 'ABXDYZ': Each letter gets index-based shift (A+1, B+2, ...)
👉 Ans: BDAGDE

Q117. Reverse 'MYSTIC' then shift alternate +2, −2
👉 Ans: EKQAWO

Q118. Sum of positions of 'DREAMS' × 2 − 3
👉 Ans: 138

Q119. Shift each letter in 'FUSION' using its ASCII mod 5
👉 Ans: GVUMRQ

Q120. 'DEVICE': +3 on 1st & 6th, −1 on 2nd & 5th, 0 on middle letters
👉 Ans: GDUHBD

Q121. 'SECRET': Reverse → shift each by its new index
👉 Ans: XJHWHZ

Q122. 'INSIGHT': +index shift
👉 Ans: JQUOJNX

Q123. ASCII sum of 'ACTION' − 100
👉 Ans: 370

Q124. Odd indices −1, Even indices +2 in 'LOGICS'
👉 Ans: KNHIDU

Q125. 'MODULE': Vowel +3, Consonant −2
👉 Ans: KPBSOH

Q126. Reverse 'PLANET' +2 shift
👉 Ans: VRGPPC

Q127. 'TARGET': Letters shifted by prime position index only
👉 Ans: TBTHGU

Q128. Shift letters of 'VECTOR' by Fibonacci sequence
👉 Ans: WGIVQU

Q129. ASCII sum of 'ENGINE', divide by 3
👉 Ans: 200

Q130. 'GRAVITY' = Shift letters by square of index mod 26
👉 Ans: GUXWJXZ

Q131. 'MARKET': First 3 reversed, last 3 +1
👉 Ans: KRAMFU

Q132. 'LUXURY' = Vowels reversed, consonants +2
👉 Ans: NWXURY

Q133. Reverse 'PYTHON', vowels +2, consonants −1
👉 Ans: MPHJRL

Q134. Shift 'CIPHER' by even-index +1, odd-index −1
👉 Ans: BJQIDQ

Q135. 'BINARY': Every third letter doubled
👉 Ans: BIIANNRRY

Q136. 'ZEBRA': Map A=Z, B=Y... reverse alphabet
👉 Ans: AVYIZ

Q137. 'JUNGLE': Odd letters +2, even letters −2
👉 Ans: LSLFJC

Q138. 'SYSTEM': Replace letters with rank of appearance (S=1st...)
👉 Ans: 123456

Q139. 'SERVER': Shift letters by mirror position from 'Z'
👉 Ans: HVEIVE

Q140. 'KERNEL': Use ASCII × index mod 26
👉 Ans: LJPLGZ

Q141. 'PYLONS': Shift by number of vowels seen so far
👉 Ans: PZMPQU

Q142. 'HEIGHT': Shift each by sum of previous ASCII
👉 Ans: IFKLLK

Q143. 'MATRIX': Add index × 2 to letter positions
👉 Ans: OEXVPZ

Q144. 'DEVICE': Reverse + even positions −3
👉 Ans: BAXFAD

Q145. 'TUNNEL': Shift using alternating sequence (1,2,3...)
👉 Ans: UVQPGQ

Q146. 'SCHOOL': Letters = frequency of first 3 letters
👉 Ans: S2H2O2

Q147. 'MODULE': Middle 2 swapped, ends +3
👉 Ans: PRDUOL

Q148. 'RECORD': Reverse + Caesar −1
👉 Ans: CPDQDB

Q149. 'PYTHON': Reverse + even index −2
👉 Ans: LRFJMP

Q150. 'LOGICAL': Shift by (index² mod 5)
👉 Ans: LRHLKCM