Coding – Master Reasoning for Competitive Exams
Boost your understanding of coding with proven strategies designed for competitive exams like SSC, UPSC, and Banking.
📚 Topic-Wise Practice Worksheets
Master Coding Decoding with our structured practice materials
Each worksheet includes detailed solutions and explanations
Letter Shift Basic Free
10 worksheets available
Letter Shift Basic problems involve shifting each letter in a word by a fixed number of positions forward or backward in the alphabet (e.g., A→D is +3 shift). This is the simplest form of coding, also known as the Caesar cipher. You must identify the shift value and apply it to new words.
Number Substitution Free
10 worksheets available
Number Substitution problems replace each letter with its position number in the alphabet (A=1, B=2, ..., Z=26). Words become sequences of numbers. Some variations use A=0, B=1, or reverse numbering (A=26, B=25). These problems test your knowledge of alphabet positions and quick conversion.
Reverse Coding Free
10 worksheets available
Reverse Coding problems involve reversing the order of letters in a word (e.g., 'CAT' becomes 'TAC'). This is the simplest pattern-based coding. You must identify that the code is the original word written backwards and apply the same operation to new words.
Opposite Letter Coding Free
10 worksheets available
Opposite Letter Coding replaces each letter with its mirror image in the alphabet, where A↔Z, B↔Y, C↔X, and so on. This is also known as the Atbash cipher. The relationship is: position of mirror letter = 27 - position of original letter.
Position Sum Free
10 worksheets available
Position Sum problems code a word by adding the position numbers of all its letters (A=1, B=2, ..., Z=26). The code is a single number representing the total sum. These problems test basic addition skills and alphabet position knowledge.
Position Arithmetic Free
10 worksheets available
Position Arithmetic problems involve performing arithmetic operations (addition, subtraction, multiplication, division) on the position numbers of letters. The result may be a new number or a transformed letter. These problems test arithmetic skills applied to alphabet positions.
Conditional Rules Free
10 worksheets available
Conditional Rules problems apply different coding rules based on letter properties (vowel/consonant, position parity, etc.). For example, vowels might be replaced by numbers while consonants are shifted. These problems test your ability to apply rule-based transformations.
Mixed Operations Free
10 worksheets available
Mixed Operations problems combine two or more coding operations in sequence (e.g., reverse the word, then shift each letter). You must identify the sequence of operations and apply them to new words. These problems test multi-step reasoning and pattern recognition.
Decode From Pattern Free
10 worksheets available
Decode from Pattern problems provide a coded word and the coding rule, and you must find the original word. This is the reverse of standard coding problems. You must apply the inverse of the coding rule to each character.
📖 Mixed Practice Worksheets
Comprehensive worksheets combining all problem types for Coding Decoding
Perfect for exam simulation and revision
Each worksheet contains 20 mixed questions covering all problem types of Coding Decoding, with detailed solutions and answer keys.
Coding-Decoding Reasoning
Coding-Decoding is a fundamental reasoning ability topic that tests your skill in deciphering patterns and rules used to transform given information (words, numbers, symbols) into codes or vice versa. Mastering this topic is essential for competitive exams as it evaluates your logical thinking, pattern recognition, and problem-solving speed.
In competitive exams, Coding-Decoding questions typically present a word, number, or symbol sequence that has been transformed using specific rules, and you must either decode it back to the original form or apply the same rules to encode another item. These questions assess your ability to identify patterns, apply logical rules, and work systematically under time pressure.
Key competitive exams featuring Coding-Decoding questions:
- SSC (CGL, CHSL, CPO, MTS, Steno)
- Banking (IBPS PO/Clerk, SBI PO, RBI Grade B)
- UPSC (CSAT Paper II)
- RRB (NTPC, Group D, ALP)
- CAT and other MBA entrance exams
- State PSCs (MPSC, UPPSC, BPSC, TNPSC)
- Defense Exams (NDA, CDS)
Types of Coding-Decoding
In this type, letters are coded based on their position in the English alphabet (A=1, B=2,..., Z=26). The coding may involve simple position values, sums of positions, or other mathematical operations.
Solved Example 1:
If "DELHI" is coded as "4-5-12-8-9", how would "MUMBAI" be coded?
- Step 1: Understand the coding pattern - each letter is represented by its position in the alphabet.
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Step 2: Verify with given example:
- D (4th letter) → 4
- E (5th) → 5
- L (12th) → 12
- H (8th) → 8
- I (9th) → 9
-
Step 3: Apply same pattern to "MUMBAI":
- M (13th letter) → 13
- U (21st) → 21
- M (13th) → 13
- B (2nd) → 2
- A (1st) → 1
- I (9th) → 9
- Answer: 13-21-13-2-1-9
Solved Example 2:
If "RAHUL" is coded as "18-1-8-21-12", decode "15-14-5-5-19-8" to get the original word.
- Step 1: Recognize the pattern - numbers represent letter positions.
-
Step 2: Verify with given example:
- R (18th letter) → 18
- A (1st) → 1
- H (8th) → 8
- U (21st) → 21
- L (12th) → 12
-
Step 3: Decode "15-14-5-5-19-8":
- 15 → O
- 14 → N
- 5 → E
- 5 → E
- 19 → S
- 8 → H
- Answer: ONEESH (Note: This is likely "ONEESH" a common Indian name)
If "BANGALORE" is coded as "2-1-14-7-1-12-15-18-5", what would be the code for "CHENNAI"?
- C (3rd), H (8th), E (5th), N (14th), N (14th), A (1st), I (9th)
- Answer: 3-8-5-14-14-1-9
In letter-shift coding, each letter of the word is moved forward or backward in the alphabet by a fixed number of positions. The shift can be consistent or follow a specific pattern.
Solved Example 1:
If "INDIA" is coded as "KQFKZ" by shifting letters forward, what would be the code for "DELHI" using the same pattern?
-
Step 1: Analyze the given coding:
- I (9) → K (11): +2
- N (14) → Q (17): +3
- D (4) → F (6): +2
- I (9) → K (11): +2
- A (1) → Z (26): +25 (or -1 considering circular alphabet)
- Step 2: The pattern appears to be +2, +3, +2, +2, -1 (alternating shifts)
-
Step 3: Apply similar pattern to "DELHI":
- D (4) +2 → F (6)
- E (5) +3 → H (8)
- L (12) +2 → N (14)
- H (8) +2 → J (10)
- I (9) -1 → H (8)
- Answer: FHNJH
Solved Example 2:
If "GOPAL" is written as "ERNYJ", how would "RAJIV" be written in the same code?
-
Step 1: Analyze letter shifts:
- G (7) → E (5): -2
- O (15) → R (18): +3
- P (16) → N (14): -2
- A (1) → Y (25): +24 (or -2 considering circular alphabet)
- L (12) → J (10): -2
- Step 2: The pattern appears to be: -2, +3, -2, -2, -2
-
Step 3: Apply to "RAJIV":
- R (18) -2 → P (16)
- A (1) +3 → D (4)
- J (10) -2 → H (8)
- I (9) -2 → G (7)
- V (22) -2 → T (20)
- Answer: PDHGT
If "MUMBAI" is coded as "OWODCK" by shifting letters, what would be the code for "KOLKATA" using the same pattern?
- Analyze MUMBAI → OWODCK:
- M (13) → O (15): +2
- U (21) → W (23): +2
- M (13) → O (15): +2
- B (2) → D (4): +2
- A (1) → C (3): +2
- I (9) → K (11): +2
- Pattern: Each letter shifted +2 positions
- Apply to KOLKATA:
- K (11) → M (13)
- O (15) → Q (17)
- L (12) → N (14)
- K (11) → M (13)
- A (1) → C (3)
- T (20) → V (22)
- A (1) → C (3)
- Answer: MQNMCVC
In number coding, words are coded based on numerical values derived from their letters. This can involve summing letter positions, using reverse positions, or other numerical operations.
Solved Example 1:
If "RANI" is coded as 34, how would "SITA" be coded following the same pattern?
-
Step 1: Analyze the given coding:
- R (18) + A (1) + N (14) + I (9) = 18+1+14+9 = 42 (but given code is 34)
- Alternative approach: Sum of reverse positions (Z=1, Y=2,..., A=26)
- R (9) + A (26) + N (13) + I (18) = 9+26+13+18 = 66 (doesn't match)
- Another approach: Sum of letter positions minus 8 (42-8=34)
- Step 2: The pattern appears to be: Sum of letter positions minus 8
-
Step 3: Apply to "SITA":
- S (19) + I (9) + T (20) + A (1) = 19+9+20+1 = 49
- 49 - 8 = 41
- Answer: 41
Solved Example 2:
If "TIGER" is coded as 62, how would "LION" be coded following the same pattern?
-
Step 1: Analyze the given coding:
- T (20) + I (9) + G (7) + E (5) + R (18) = 20+9+7+5+18 = 59 (but code is 62)
- Alternative approach: Sum of letter positions plus 3 (59+3=62)
- Step 2: The pattern appears to be: Sum of letter positions plus 3
-
Step 3: Apply to "LION":
- L (12) + I (9) + O (15) + N (14) = 12+9+15+14 = 50
- 50 + 3 = 53
- Answer: 53
If "PEACOCK" is coded as 62 and "PARROT" as 78, what would be the code for "SPARROW" following the same pattern?
- Analyze given examples:
- PEACOCK: P(16)+E(5)+A(1)+C(3)+O(15)+C(3)+K(11) = 54 → code is 62 (difference +8)
- PARROT: P(16)+A(1)+R(18)+R(18)+O(15)+T(20) = 88 → code is 78 (difference -10)
- Alternative pattern: Sum of letters minus number of vowels
- PEACOCK: 54 - 3 vowels (E,A,O) = 51 (doesn't match 62)
- Another approach: Sum of letters plus number of consonants
- PEACOCK: 54 + 4 consonants (P,C,C,K) = 58 (doesn't match)
- Alternative solution: Sum of letters plus 2×number of vowels
- PEACOCK: 54 + (2×3) = 60 (doesn't match)
- Likely pattern: Sum of letters plus position of first vowel (E is 5th letter) minus 1
- PEACOCK: 54 + 2 (E is 2nd letter) = 56 (doesn't match)
- Given inconsistency, this appears to be a challenging question requiring additional information
- Note: This demonstrates that not all patterns are immediately obvious, and sometimes questions may require more information or have multiple possible interpretations.
In mixed coding, words are coded using a combination of letters and numbers based on specific rules that may involve both letter positions and numerical operations.
Solved Example 1:
If "INDIA" is coded as "I2D4A", how would "BHARAT" be coded following the same pattern?
-
Step 1: Analyze the given coding:
- I (9) → I
- N (14) → 2 (sum of digits: 1+4=5, but given is 2 - possible position in word?)
- D (4) → D
- I (9) → 4 (sum of digits: 9 → 9, but given is 4 - perhaps position in word?)
- A (1) → A
-
Step 2: Alternative pattern: Vowels remain as letters, consonants replaced by their position in the word
- I (vowel, 1st letter) → I
- N (consonant, 2nd letter) → 2
- D (consonant, 3rd letter) → D (but given as D, not 3)
-
Step 3: Another approach: First and last letters remain, others replaced by their position in alphabet
- I (9) → I
- N (14) → 14 → sum of digits 1+4=5 (doesn't match given 2)
-
Step 4: Most plausible pattern: First, middle, and last letters remain as letters, others replaced by their position in the word
- INDIA (5 letters): Positions 1(I), 3(D), 5(A) remain; positions 2(N) and 4(I) become their position numbers
- Thus: I, 2, D, 4, A → I2D4A
-
Step 5: Apply to "BHARAT":
- B (1), H (2), A (3), R (4), A (5), T (6)
- Positions to remain: 1(B), 3(A), 6(T)
- Positions to replace: 2(H)→2, 4(R)→4, 5(A)→5
- Thus: B, 2, A, 4, 5, T → B2A45T
- Answer: B2A45T
Solved Example 2:
If "MOHAN" is coded as "M16H1N14", how would "SURESH" be coded following the same pattern?
-
Step 1: Analyze the given coding:
- M → M
- O → 16 (16th letter is P, but O is 15th)
- H → H
- A → 1 (A is 1st letter)
- N → N14 (N is 14th letter)
-
Step 2: The pattern appears to be: Vowels are replaced by their positions, consonants remain as letters followed by their positions
- M (consonant) → M13 (but given M)
- O (vowel) → 15 (but given 16)
- Alternative pattern: Alternate letters are replaced by their positions
- M (1st) → M
- O (2nd) → 15 (but given 16)
- H (3rd) → H
- A (4th) → 1
- N (5th) → N14
-
Step 3: Most plausible pattern: First and third letters remain as letters, others are replaced by their positions in alphabet
- M → M
- O → 15 (but given 16 - possible error in question)
- Assuming pattern is: First and alternate letters remain, others show their positions
- M → M
- O → 15
- H → H
- A → 1
- N → N14
-
Step 4: Apply similar pattern to "SURESH":
- S → S
- U → 21
- R → R
- E → 5
- S → S
- H → H8
- Thus: S21R5SH8
- Answer: S21R5SH8
If "KAVERI" is coded as "K22V5R9", how would "GODAVARI" be coded following the same pattern?
- Analyze KAVERI → K22V5R9:
- K → K
- A → 22 (A is 1st, not 22)
- V → V
- E → 5 (E is 5th)
- R → R
- I → 9 (I is 9th)
- Pattern appears to be: Consonants remain as letters, vowels replaced by their positions plus 21
- A (1) → 1+21=22
- E (5) → 5+21=26 (but given 5)
- Alternative pattern: Alternate letters show positions
- K (1st) → K
- A (2nd) → 1 (A's position in alphabet)
- V (3rd) → V
- E (4th) → 5 (E's position)
- R (5th) → R
- I (6th) → 9 (I's position)
- Thus for GODAVARI:
- G → G
- O → 15
- D → D
- A → 1
- V → V
- A → 1
- R → R
- I → 9
- Answer: G15D1V1R9
In symbol coding, letters or words are represented by various symbols based on specific rules. The coding may involve direct symbol substitution or more complex relationships between letters and symbols.
Solved Example 1:
In a certain code, "APPLE" is written as "%@@#&" and "GRAPE" is written as "*%#@&". How would "PEAR" be written in this code?
-
Step 1: Align letters with symbols for both words:
Letter A P P L E Symbol % @ @ # & Letter G R A P E Symbol * % # @ & -
Step 2: Identify consistent symbol-letter pairs:
- A: % (from APPLE) but # (from GRAPE) → inconsistency
- P: @ (both cases)
- E: & (both cases)
- L: # (only in APPLE)
- G: * (only in GRAPE)
- R: % (only in GRAPE)
- Step 3: Possible pattern: Symbols represent letter shapes or phonetic elements rather than direct substitution
-
Step 4: Alternative approach: Symbols represent letter positions in reverse (Z=1, Y=2,..., A=26)
- A (26) → % (ASCII 37)
- P (11) → @ (ASCII 64)
- No clear correlation
-
Step 5: Given complexity, likely that each symbol corresponds to a specific letter:
- From APPLE: P=@, E=&
- From GRAPE: G=*, R=%, A=#, P=@, E=&
- Thus:
- P = @
- E = &
- A = # (from GRAPE, overriding % from APPLE)
- R = %
-
Step 6: Code "PEAR":
- P → @
- E → &
- A → #
- R → %
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Sandeep Nehra
B.Tech (Mech) | MBA (HRM & IB) | Lead Developer & Reasoning Expert (16+ Yrs)
Sandeep is a Mechanical Engineer and dual MBA (HR & International Business) with over 16 years of experience as a Senior Web Architect and Tech Lead. Combining his engineering precision with deep behavioral insights, he founded ReasoningAbility.com to revolutionize competitive exam preparation. His unique methodology — blending logical structuring from engineering with psychological clarity from HRM — helps aspirants crack BITSAT, SSC, and Banking exams faster. His mission remains simple: provide high-quality, free practice resources that turn complex logic into accessible, high-speed solving techniques for students worldwide.