Easy #1
Encoded: 182114
Key: 1=A, 2=B, 3=C, ... 26=Z
A. BOX
B. OWL
C. RUN
D. CAT
Answer: C
Explanation:
Code type: Number to Letter Decoding step by step: "182114" → "RUN"
Coding & Decoding Practice Questions with Answers
Practice with 30 sample questions organized by difficulty. Click “Show Answer” to reveal the correct answer and explanation.
Easy
Easy #2
Encoded: 16514
Key: A=1, B=2, C=3, ... Z=26
A. RED
B. KEY
C. FLY
D. PEN
Answer: D
Explanation:
Code type: Letter to Number Decoding step by step: "16514" → "PEN"
Easy #3
Encoded: 32116
Key: A=1, B=2, C=3, ... Z=26
A. CAT
B. FOX
C. BOX
D. CUP
Answer: D
Explanation:
Code type: Letter to Number Decoding step by step: "32116" → "CUP"
Easy #4
Encoded: 32116
Key: 1=A, 2=B, 3=C, ... 26=Z
A. CUP
B. MAP
C. FLY
D. RUN
Answer: A
Explanation:
Code type: Number to Letter Decoding step by step: "32116" → "CUP"
Easy #5
Encoded: DER
Key: Spell the word backwards
A. RED
B. BOX
C. HAT
D. PEN
Answer: A
Explanation:
Code type: Reverse Word Decoding step by step: "DER" → "RED"
Easy #6
Encoded: 3120
Key: A=1, B=2, C=3, ... Z=26
A. FLY
B. CAT
C. FOX
D. CUP
Answer: B
Explanation:
Code type: Letter to Number Decoding step by step: "3120" → "CAT"
Easy #7
Encoded: 8120
Key: A=1, B=2, C=3, ... Z=26
A. MAP
B. CUP
C. HAT
D. PEN
Answer: C
Explanation:
Code type: Letter to Number Decoding step by step: "8120" → "HAT"
Easy #8
Encoded: 16514
Key: 1=A, 2=B, 3=C, ... 26=Z
A. CAT
B. DOG
C. HAT
D. PEN
Answer: D
Explanation:
Code type: Number to Letter Decoding step by step: "16514" → "PEN"
Easy #9
Encoded: NUR
Key: Spell the word backwards
A. RUN
B. FOX
C. SUN
D. DOG
Answer: A
Explanation:
Code type: Reverse Word Decoding step by step: "NUR" → "RUN"
Easy #10
Encoded: 11525
Key: A=1, B=2, C=3, ... Z=26
A. RUN
B. FLY
C. KEY
D. CAT
Answer: C
Explanation:
Code type: Letter to Number Decoding step by step: "11525" → "KEY"
Medium
Medium #11
Encoded: WZIP
Key: A=Z, B=Y, C=X, D=W, ...
A. TREE
B. SNOW
C. BIRD
D. DARK
Answer: D
Explanation:
Code type: Atbash Cipher Decoding step by step: "WZIP" → "DARK"
Medium #12
Encoded: NLLM
Key: A=Z, B=Y, C=X, D=W, ...
A. MOON
B. BIRD
C. RAIN
D. DARK
Answer: A
Explanation:
Code type: Atbash Cipher Decoding step by step: "NLLM" → "MOON"
Medium #13
Encoded: XYFW
Key: A=F, B=G, C=H, D=I, E=J, ...
A. WIND
B. FISH
C. TREE
D. STAR
Answer: D
Explanation:
Code type: Caesar Cipher Decoding step by step: "XYFW" → "STAR"
Medium #14
Encoded: UVCT
Key: A=C, B=D, C=E, D=F, E=G, ...
A. FISH
B. MOON
C. STAR
D. FIRE
Answer: C
Explanation:
Code type: Caesar Cipher Decoding step by step: "UVCT" → "STAR"
Medium #15
Encoded: 2583
Key: Phone: A-C=2, D-F=3, G-I=4, J-L=5, M-O=6, P-S=7, T-V=8, W-Z=9
A. WIND
B. MOON
C. BLUE
D. BIRD
Answer: C
Explanation:
Code type: Phone Keypad Code Decoding step by step: "2583" → "BLUE"
Medium #16
Encoded: VTFF
Key: Vowels (A,E,I,O,U) +1, Consonants +2
A. WIND
B. FISH
C. TREE
D. GOLD
Answer: C
Explanation:
Code type: Vowel-Consonant Code Decoding step by step: "VTFF" → "TREE"
Medium #17
Encoded: 44 42 15 15
Key: 5×5 grid: A=11, B=12, ... I/J=24, ... Z=55
A. TREE
B. WIND
C. GOLD
D. RAIN
Answer: A
Explanation:
Code type: Polybius Square Decoding step by step: "44 42 15 15" → "TREE"
Medium #18
Encoded: ZBBA
Key: ROT13 (shift by 13)
A. FIRE
B. BIRD
C. MOON
D. BLUE
Answer: C
Explanation:
Code type: ROT13 Decoding step by step: "ZBBA" → "MOON"
Medium #19
Encoded: 7827
Key: Phone: A-C=2, D-F=3, G-I=4, J-L=5, M-O=6, P-S=7, T-V=8, W-Z=9
A. MOON
B. SNOW
C. STAR
D. GOLD
Answer: C
Explanation:
Code type: Phone Keypad Code Decoding step by step: "7827" → "STAR"
Medium #20
Encoded: WDLS
Key: Vowels (A,E,I,O,U) +3, Consonants +5
A. RAIN
B. TREE
C. FIRE
D. BIRD
Answer: A
Explanation:
Code type: Vowel-Consonant Code Decoding step by step: "WDLS" → "RAIN"
Hard
Hard #21
Encoded: RVRIE
Key: Rail Fence (2 rails): zigzag then read rows
A. CLOUD
B. RIVER
C. EARTH
D. WATER
E. FROST
Answer: B
Explanation:
Code type: Rail Fence Cipher Decoding step by step: "RVRIE" → "RIVER"
Hard #22
Encoded: HSDXT
Key: Shift 2 position(s) right on keyboard row
A. GRASS
B. MUSIC
C. LIGHT
D. STORM
E. FLAME
Answer: E
Explanation:
Code type: Keyboard Cipher Decoding step by step: "HSDXT" → "FLAME"
Hard #23
Encoded: MTLEA
Key: Rail Fence (2 rails): zigzag then read rows
A. FLAME
B. GRASS
C. CLOUD
D. METAL
E. PLANT
Answer: D
Explanation:
Code type: Rail Fence Cipher Decoding step by step: "MTLEA" → "METAL"
Hard #24
Encoded: ORTSG
Key: A=Z, B=Y, C=X, D=W, ...
A. FROST
B. STORM
C. WATER
D. STONE
E. LIGHT
Answer: E
Explanation:
Code type: Atbash Cipher Decoding step by step: "ORTSG" → "LIGHT"
Hard #25
Encoded: PVMCX
Key: Vigenère key: KEY
A. LIGHT
B. FROST
C. METAL
D. RIVER
E. DREAM
Answer: B
Explanation:
Code type: Vigenère Cipher Decoding step by step: "PVMCX" → "FROST"
Hard #26
Encoded: EFBBA
Key: Vigenère key: BOX
A. MUSIC
B. RIVER
C. DREAM
D. PLANT
E. STORM
Answer: C
Explanation:
Code type: Vigenère Cipher Decoding step by step: "EFBBA" → "DREAM"
Hard #27
Encoded: TEMHL
Key: Vigenère key: HAT
A. WATER
B. LIGHT
C. METAL
D. STORM
E. FROST
Answer: C
Explanation:
Code type: Vigenère Cipher Decoding step by step: "TEMHL" → "METAL"
Hard #28
Encoded: WPDDI
Key: Vigenère key: RED
A. PLANT
B. FLAME
C. LIGHT
D. STORM
E. FROST
Answer: B
Explanation:
Code type: Vigenère Cipher Decoding step by step: "WPDDI" → "FLAME"
Hard #29
Encoded: OENCA
Key: Take positions 1,3,5... then 2,4,6...
A. METAL
B. FROST
C. STONE
D. OCEAN
E. RIVER
Answer: D
Explanation:
Code type: Skip Cipher Decoding step by step: "OENCA" → "OCEAN"
Hard #30
Encoded: VWRUP
Key: A=@, B=!, C=+, D=$, E=%, F=&, ...
A. EARTH
B. STORM
C. DREAM
D. CLOUD
E. METAL
Answer: B
Explanation:
Code type: Symbol Code Decoding step by step: "VWRUP" → "STORM"
Frequently Asked Questions
You'll encounter letter-to-number codes (A=1, B=2), reverse alphabet (A=Z, B=Y), shifted alphabets (each letter replaced by one N positions away), and symbol substitutions. Harder levels combine multiple rules.
Government agencies, civil service, banks, military, intelligence services, and organizations requiring security clearance. These tests are common in IBPS, SSC, and other competitive exams in many countries.
First, understand the code rule by examining the key carefully. Apply the rule letter by letter. For complex codes, write down intermediate steps. Check your answer by encoding it back to verify.
Each code system is procedurally generated using random substitution rules. The system selects a cipher type (letter shift, number mapping, reverse alphabet, or symbol substitution), applies it consistently to create encoded words, and generates distractors that contain specific decoding errors. Harder levels combine multiple rules. This ensures every question is unique.