Coding-Decoding & Symbol Series - Complete SSC CGL Guide
What is Coding-Decoding? It's a reasoning ability topic where letters/words are coded using specific patterns/rules. Your task is to decode the pattern and apply it to new words. Symbol series involves identifying patterns in symbol sequences.
Each letter is coded using a specific pattern. Find the pattern from given example.
Pro Tip – The 3-Step Coding Decoding Method!
1. Analyze: Study given coded-decoded pair to find pattern
2. Verify: Apply pattern to other given words to confirm
3. Apply: Use pattern to code/decode required word
Visit SKY Practice for 300+ Coding-Decoding questions with detailed solutions.
1. Coding-Decoding Basics
What is Coding? Coding means converting a word/letter into another form using specific rules. Decoding means converting it back to original form by understanding the pattern.
Understanding Coding Formats
Types of Coding in SSC CGL
SSC tests coding-decoding in various formats: letter coding, number coding, symbol coding, and mixed patterns.
Letter Coding
- Forward/Backward shifting of letters
- Opposite letter coding
- Vowel/Consonant coding
- Letter position coding
- Letter to letter coding
- Word to word coding
Number Coding
- Letter position sums/differences
- Word to number coding
- Number to letter coding
- Mathematical operations
- Position based coding
- Mixed number patterns
Symbol Coding
- Letter to symbol coding
- Word to symbol coding
- Symbol operations
- Symbol series patterns
- Conditional symbol coding
- Mixed symbol patterns
Mixed Coding
- Letter + number coding
- Symbol + letter coding
- Condition based coding
- Multiple step coding
- Reverse pattern coding
- Complex rule based coding
SSC Shortcut: Pattern Identification
Check letter positions: A=1, B=2, Z=26 (reverse: Z=1, A=26)
Look for arithmetic patterns: +1, -1, +2, -2, ×2, ÷2
Check vowel-consonant patterns: Vowels coded differently
Verify with multiple examples: Always test pattern on 2+ examples
Watch for reverse coding: Sometimes pattern works backwards
Check letter opposites: A↔Z, B↔Y, C↔X pattern
Solved Example: Basic Letter Coding
CAT → DBU
Break down letter by letter:
C → D (C+1)
A → B (A+1)
T → U (T+1)
Pattern: Each letter moves forward by 1 position
Step 2: Verify pattern consistency
All three letters follow same pattern (+1)
Pattern confirmed: Forward shift by 1
Step 3: Apply pattern to DOG
D → E (D+1)
O → P (O+1)
G → H (G+1)
Result: EPH
Step 4: Double-check
D(4) → E(5): +1 ✓
O(15) → P(16): +1 ✓
G(7) → H(8): +1 ✓
Step 5: Write final answer
DOG is coded as EPH
Step 6: Alternative verification
Could test with another word if available
If BAT → CBU (B+1, A+1, T+1) pattern holds
Final Answer: EPH
Alphabet Position Reference
Memorize these positions - they're essential for solving coding problems quickly
2. Letter Coding Patterns
Letter Coding: Most common type where letters are coded using various patterns based on their positions, relationships, or other rules.
Common Letter Coding Patterns
Frequency of Letter Coding Types in SSC CGL
Based on analysis of previous 5 years' papers, these are the most common letter coding patterns.
Letter Coding Pattern Frequency in SSC CGL
Forward/Backward Shift
• Reverse: -1, -2, -3, etc.
• Variable: Different shifts for each letter
• Conditional: Vowels/consonants different
• Pattern: +1, +2, +1, +2 alternating
Examples:
CAT → DBU (+1 each)
ZOO → APP (Z→A, O→P, O→P)
BAT → DCV (+2 each)
Opposite Letter Coding
• Position sum = 27 (A=1, Z=26)
• Formula: Opposite = 27 - position
• Sometimes +1 after opposite
• Can be vowel-specific opposite
Examples:
ABC → ZYX (A↔Z, B↔Y, C↔X)
MAN → NZM (M↔N, A↔Z, N↔M)
CAT → XZG (C↔X, A↔Z, T↔G)
Position Based Coding
- Letter position in alphabet
- Sum of positions
- Product of positions
- Difference between positions
- Square of position
- Position with operations
CAT → 3×1×20 = 60 (product)
DOG → (4-15-7) difference pattern
Vowel/Consonant Different
- Vowels coded differently than consonants
- Vowels forward, consonants backward
- Vowels become numbers
- Consonants become symbols
- Vowels +1, consonants -1
- Special vowel coding rules
Vowels become numbers
Consonants become symbols
1 Forward Shift Pattern Rules
• +2 shift: A→C, B→D, ..., Y→A, Z→B
• +N shift: Add N to position, mod 26
• Watch for: Z→A special case
• Example: +3 shift: A→D, B→E, ..., X→A, Y→B, Z→C
Quick calculation:
New position = (Old position + N - 1) % 26 + 1
Where % is modulo (remainder)
Verification trick: Test with A and Z
If A→C and Z→B, pattern is consistent (+2)
2 Opposite Letter Rules
• Position sum = 27 (1+26=27, 2+25=27, etc.)
• Formula: Opposite position = 27 - current position
• Quick method: Count from opposite end
Memory trick: First half ↔ Second half reversed
A(1) ↔ Z(26), B(2) ↔ Y(25), C(3) ↔ X(24), ...
Verification: Test with A and M
A→Z ✓, M→N ✓ (M=13, N=14, sum=27)
Common variation: Opposite then +1
Example: A→Z→A (opposite then +1 = A)
Solved Example: Complex Letter Coding
WORK → XNSJ
Break down letter by letter:
W → X (W+1)
O → N (O-1)
R → S (R+1)
K → J (K-1)
Pattern: Alternating +1, -1, +1, -1
Step 2: Verify pattern
Positions: W(23)→X(24): +1 ✓
O(15)→N(14): -1 ✓
R(18)→S(19): +1 ✓
K(11)→J(10): -1 ✓
Pattern confirmed: +1, -1, +1, -1 alternating
Step 3: Apply pattern to PLAY
P → Q (P+1) [1st letter: +1]
L → K (L-1) [2nd letter: -1]
A → B (A+1) [3rd letter: +1]
Y → X (Y-1) [4th letter: -1]
Result: QKBX
Step 4: Double-check positions
P(16)→Q(17): +1 ✓
L(12)→K(11): -1 ✓
A(1)→B(2): +1 ✓
Y(25)→X(24): -1 ✓
Step 5: Verify with another word
Test with "BALL":
B→C (+1), A→Z (-1), L→M (+1), L→K (-1)
BALL → CZMK (follows pattern)
Step 6: Write final answer
PLAY is coded as QKBX
Pattern identification tip:
When pattern alternates, check odd/even positions
Here: Odd positions (1st, 3rd): +1
Even positions (2nd, 4th): -1
Final Answer: QKBX
3. Number Coding Patterns
Number Coding: Letters/words are coded as numbers using their positions, sums, products, or other mathematical operations.
Common Number Coding Patterns
Number Coding Approaches
These patterns convert letters to numbers based on their alphabet positions and mathematical relationships.
Sum of Positions
- Simple sum: A=1, B=2, ... sum all
- Vowels only sum
- Consonants only sum
- First & last letter sum
- Middle letters sum
- Weighted sum (position × factor)
DOG = 4+15+7 = 26
Vowels only: CAT = A=1 → 1
Product of Positions
- Simple product: multiply all positions
- Vowels product
- Consonants product
- First × last
- Alternating product
- Position squares product
BAT = 2×1×20 = 40
First×last: CAT = 3×20 = 60
Difference Patterns
- Difference between letters
- First - last
- Vowel - consonant differences
- Alternating differences
- Absolute differences
- Cumulative differences
First-last: C-T=3-20=-17
Absolute: |C-A|=2, |A-T|=19
Complex Operations
- Sum then multiply
- Product then add constant
- Position squares sum
- Cube roots etc.
- Multiple step operations
- Conditional operations
DOG: 4²+15²+7² = 16+225+49=290
BAT: (2×1)+20 = 22
SSC Shortcut: Number Coding Quick Methods
Sum pattern: Add all positions (A=1 to Z=26)
Product pattern: Multiply all positions (watch for large numbers)
Difference pattern: Usually first-last or consecutive differences
Square pattern: Sum of squares of positions
Vowel/consonant separate: Different operations for vowels vs consonants
Test with simple words: Use CAT, BAT, DOG to identify pattern
Solved Example: Number Coding
CAT → 24
DOG → 26
Step 2: Find letter positions
CAT: C=3, A=1, T=20 → Sum = 3+1+20 = 24 ✓
DOG: D=4, O=15, G=7 → Sum = 4+15+7 = 26 ✓
Pattern: Sum of alphabet positions
Step 3: Verify pattern
Test with another word if possible
RAT: R=18, A=1, T=20 → Sum = 39
Pattern consistent
Step 4: Apply pattern to BAT
BAT: B=2, A=1, T=20
Sum = 2 + 1 + 20 = 23
Step 5: Double-check
B(2)+A(1)+T(20) = 23 ✓
Step 6: Consider alternative patterns
Could it be product? CAT=3×1×20=60 ✗ (not 24)
Could it be average? CAT=(3+1+20)/3=8 ✗ (not 24)
Sum pattern is confirmed
Step 7: Write final answer
BAT is coded as 23
Pattern identification tip:
When numbers are relatively small (20-30), likely sum of positions
When numbers are large (100+), likely product or squares
Final Answer: 23
Solved Example: Complex Number Coding
CAT → 60
BAT → 40
Step 2: Find letter positions
CAT: C=3, A=1, T=20
BAT: B=2, A=1, T=20
Step 3: Check sum pattern
CAT sum = 3+1+20 = 24 ✗ (not 60)
BAT sum = 2+1+20 = 23 ✗ (not 40)
Not sum pattern
Step 4: Check product pattern
CAT product = 3×1×20 = 60 ✓
BAT product = 2×1×20 = 40 ✓
Pattern: Product of alphabet positions
Step 5: Verify pattern
Test with DOG: D=4, O=15, G=7 → 4×15×7=420
Pattern holds
Step 6: Apply pattern to RAT
RAT: R=18, A=1, T=20
Product = 18 × 1 × 20 = 360
Step 7: Double-check calculation
18 × 1 = 18
18 × 20 = 360 ✓
Step 8: Write final answer
RAT is coded as 360
Pattern identification tip:
When numbers are exactly product of positions (60=3×20, 40=2×20)
And A=1 always, so product = (first letter position) × 20
Because A=1 and T=20, product = first letter × 1 × 20 = first letter × 20
Quick method:
For words ending with AT: code = (first letter position) × 20
CAT: 3×20=60, BAT: 2×20=40, RAT: 18×20=360
Final Answer: 360
4. Symbol Coding & Operations
Symbol Coding: Letters/words are coded using symbols (★, ●, ▲, etc.) with specific operations or patterns.
Symbol Coding Patterns
Understanding Symbol Operations
Symbols represent operations (+, -, ×, ÷) or have fixed values. Your task is to decode the symbol meanings.
If ★ + ● = 8, and ★ = 3, then ● = 5
Symbol as Operations
- Symbols = +, -, ×, ÷ operations
- Multiple symbols in equation
- Symbols have fixed values
- Symbols follow BODMAS rules
- Symbols in equations
- Solve for symbol values
● = 10 - 6 = 4
Letter to Symbol Coding
- Each letter has fixed symbol
- Vowels different symbols
- Consonants different symbols
- Position based symbols
- Word to symbol sequence
- Reverse symbol coding
BAD = ●★■
Symbol Equations
- Solve symbol equations
- Find symbol values
- Multiple equations
- Symbol relationships
- Word problems with symbols
- Complex symbol systems
★ - ● = 5
Find ★ and ●
★=10, ●=5
Conditional Symbol Coding
- If-then symbol rules
- Multiple conditions
- Symbol depends on position
- Odd/even position symbols
- Vowel/consonant symbols
- Complex rule systems
CAT = ●★●
SSC Shortcut: Symbol Problem Solving
Start with what you know: Use given equations to find values
Substitution method: Substitute known values into equations
Look for patterns: Same symbol always has same value
Check all equations: Solution must satisfy all given equations
Test with simple values: Try 0, 1, 2 for unknown symbols
Watch for BODMAS: Remember operation order in equations
Solved Example: Symbol Operations
Let ★ = x, ● = y
Equation 1: x + y = 10
Equation 2: x × y = 24
Step 2: Solve system
From equation 1: y = 10 - x
Substitute in equation 2: x(10 - x) = 24
10x - x² = 24
x² - 10x + 24 = 0
Step 3: Solve quadratic
x² - 10x + 24 = 0
(x - 4)(x - 6) = 0
x = 4 or x = 6
Step 4: Find corresponding y values
If x = 4, then y = 10 - 4 = 6
If x = 6, then y = 10 - 6 = 4
Both solutions: (4,6) or (6,4)
Step 5: Check with both equations
Solution 1: ★=4, ●=6
4+6=10 ✓, 4×6=24 ✓
Solution 2: ★=6, ●=4
6+4=10 ✓, 6×4=24 ✓
Step 6: Write final answer
★ = 4 and ● = 6
Or ★ = 6 and ● = 4
Both are correct
Alternative quick method:
Think of pairs that multiply to 24 and add to 10:
1×24=24, sum=25 ✗
2×12=24, sum=14 ✗
3×8=24, sum=11 ✗
4×6=24, sum=10 ✓
So numbers are 4 and 6
Final Answer: ★ = 4, ● = 6 (or vice versa)
5. Symbol Series Patterns
Symbol Series: Identify the pattern in a sequence of symbols and find the missing symbol or next symbol in series.
Symbol Series Patterns
Common Symbol Series Types
Symbols follow patterns based on position, rotation, alternation, or mathematical rules.
Pattern: Alternating ▲ and ▼. Next symbol should be ▲
Alternating Patterns
- Two symbols alternating
- Three symbols rotating
- Group alternation
- Position based alternation
- Skip pattern alternation
- Complex alternation
★●■★●■? (Next: ★)
▲▲▼▼▲▲? (Next: ▼)
Rotation Patterns
- Symbol rotation by degrees
- Clockwise rotation
- Anti-clockwise rotation
- Flip/reflection patterns
- Position change patterns
- Complex transformations
⬆︎→⬇︎←? (Next: ⬆︎) clockwise
◢◣◤◥? (Next: ◢) rotation
Increasing/Decreasing
- Number of elements increases
- Size of symbols changes
- Shading intensity changes
- Position movement
- Complex progression
- Geometric progression
▲ △ ▲ △ ? (Size alternation)
○ ● ○ ● ? (Shading alternation)
Mathematical Patterns
- Symbols represent numbers
- Arithmetic operations
- Position calculations
- Skip counting patterns
- Prime number patterns
- Fibonacci type patterns
★ ● ■ ★ ● ? (Next: ■)
Pattern: 1,2,3,1,2,3...
Step 1: Look for Simple Alternation
Check if symbols alternate in a simple pattern (ABAB, ABCABC, etc.)
Step 2: Check Rotation/Transformation
See if symbols are rotating, flipping, or changing in a systematic way
Step 3: Look for Group Patterns
Check if symbols form groups that repeat (AABB, ABCC, etc.)
Step 4: Check Position Based
See if symbol depends on its position in the series
Step 5: Consider Mathematical
Symbols might represent numbers following arithmetic patterns
Solved Example: Symbol Series
Series: ▲ ▼ ▶︎ ◀︎ ▲ ▼ ▶︎ ?
Write positions: 1:▲, 2:▼, 3:▶︎, 4:◀︎, 5:▲, 6:▼, 7:▶︎, 8:?
Step 2: Look for simple alternation
Not simple ABAB (▲▼▲▼...)
Not ABCABC (▲▼▶︎▲▼▶︎... would be 6 symbols repeating)
Step 3: Check group patterns
Group of 4: ▲▼▶︎◀︎ then repeats: ▲▼▶︎◀︎
But we have: ▲▼▶︎◀︎▲▼▶︎?
First group: ▲▼▶︎◀︎ (4 symbols)
Second group started: ▲▼▶︎? (3 symbols so far)
If pattern is groups of 4 repeating, next should be ◀︎
Step 4: Verify pattern
Pattern: ▲▼▶︎◀︎ repeats
Positions 1-4: ▲▼▶︎◀︎
Positions 5-8: ▲▼▶︎◀︎ (expected)
Position 7: ▶︎ ✓
Position 8: should be ◀︎
Step 5: Consider alternative patterns
Could be rotation pattern? ▲▼▶︎◀︎ are arrows pointing up, down, right, left
Sequence: up, down, right, left, up, down, right, left...
This matches our identified pattern
Step 6: Write final answer
Next symbol is ◀︎ (left arrow)
Pattern identification:
This is a 4-symbol rotation sequence: up→down→right→left→repeat
Common arrow direction pattern
Memory tip:
Arrow sequences often follow compass directions: N,S,E,W or up,down,right,left
Final Answer: ◀︎
6. SSC Shortcuts & Time-Saving Techniques
Exam-Focused Strategies: These shortcuts help solve coding-decoding questions quickly in SSC exams.
Time-Saving Coding Techniques
Speed vs Accuracy Balance
In SSC exams, you need to solve coding questions quickly without sacrificing accuracy. These techniques help achieve that balance.
Quick Letter Position
• Quick calculation: B=2, Y=25, etc.
• Opposite pairs: A-Z, B-Y, C-X
• Sum 27 trick: Position + Opposite = 27
• Vowels: A=1, E=5, I=9, O=15, U=21
• Consonants: Learn key positions
Time saver: Don't count from A each time
Pattern Recognition
- +1/-1 patterns most common
- Alternating patterns (+1,-1,+1,-1)
- Opposite letter patterns (A↔Z)
- Sum patterns for number coding
- Product patterns for larger numbers
- Vowel/consonant different coding
Verification Methods
- Test pattern with 2+ examples
- Check with extreme letters (A,Z)
- Verify with vowels and consonants
- Test backward application
- Check all given information
- Look for inconsistencies
Time Management
• Medium questions: 45 seconds
• Hard questions: 60 seconds max
• If stuck > 90 sec, guess and move
• Practice with timer daily
• Learn to recognize quick-solve patterns
Priority: Do easy coding first, hard ones last
SSC Shortcut: Common Coding Patterns to Memorize
Pattern 1: +1 forward shift (CAT → DBU) - Most common
Pattern 2: Opposite letters (A↔Z, B↔Y) - Very common
Pattern 3: Sum of positions (CAT → 3+1+20=24)
Pattern 4: Alternating +1,-1 (WORK → XNSJ)
Pattern 5: Vowels +1, consonants -1 (or vice versa)
Pattern 6: First+last, middle letters special coding
Pattern 7: Letter to number to symbol mixed coding
Pattern 8: Symbol series: alternation, rotation, groups
SSC Shortcut: Elimination Method for MCQs
Step 1: Solve the question independently first
Step 2: If confident, select your answer directly
Step 3: If unsure, eliminate obviously wrong options
Step 4: Test remaining options with pattern
Step 5: Choose most logical option
Step 6: If still stuck, guess from remaining options
Step 7: Never leave any question unanswered
7. Practice MCQs & Exercises
Hands-on Practice: Apply what you've learned with these SSC-level coding-decoding and symbol series questions.
Interactive Practice Questions
Practice Approach
Time yourself: 45 seconds per coding question, 30 seconds per symbol series. Apply the strategies systematically.
Practice Question 1: Letter Coding
Practice Question 2: Number Coding
Practice Question 3: Symbol Series
Practice Question 4: Mixed Coding
SSC Shortcut: Practice Strategy
Daily practice: 10 coding + 5 symbol series daily
Pattern notebook: Record new patterns you encounter
Time yourself: Practice with 45-second timer
Previous papers: Solve last 5 years' SSC coding questions
Error analysis: Review mistakes to avoid repetition
Mixed practice: Practice all types randomly
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Frequently Asked Questions
Q1: How many coding-decoding questions in SSC CGL?
Answer: Typically 4-6 questions in Tier I. These include letter coding, number coding, symbol coding, and mixed patterns.
Q2: What's the most common coding pattern in SSC?
Answer: Forward/backward letter shift (+1/-1 patterns) are most common (appear in 90% of papers), followed by opposite letter coding (80%).
Q3: How to quickly solve symbol series questions?
Answer: Look for: 1) Simple alternation, 2) Rotation patterns, 3) Group repetition, 4) Increasing/decreasing elements. Start with simplest pattern first.
Q4: What if I can't identify the pattern?
Answer: Try these: 1) Check +1/-1 shifts, 2) Check opposite letters, 3) Check sum of positions, 4) Test vowel/consonant different coding. If still stuck, eliminate options and guess.
Q5: How much time per coding question?
Answer: Target 45 seconds for coding, 30 seconds for symbol series. If stuck for >90 seconds, make educated guess and move on.
Q6: Best way to improve coding-decoding speed?
Answer: Practice daily with timer, memorize alphabet positions, learn common patterns, solve previous year papers, maintain error log.
Final Exam Strategy for Coding-Decoding
Time Allocation: Coding: 45 seconds, Symbol Series: 30 seconds maximum.
Priority Order: 1) Simple letter coding, 2) Symbol series, 3) Number coding, 4) Complex mixed coding.
Accuracy Check: Always verify pattern with 2+ examples before final answer.
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