Coding-Decoding Quick Revision Sheet for RRB
Key Concepts
- Coding: Converting a word/letter into another form using a specific rule.
- Decoding: Reversing the coding rule to get the original word/letter.
- Types: Letter, Number, Symbol, Mixed, Matrix & Substitution.
Letter-to-Letter Rules (Must-Memorize)
| Rule Name |
Trick |
Example |
| +n shift |
“A+1=B, B+1=C…” |
CODE → DPEF (+1) |
| –n shift |
“Z–1=Y, Y–1=X…” |
ZOO → YNN (–1) |
| Reverse |
“A↔Z, B↔Y…” (A=1, Z=26) |
AZ → ZA |
| Position-sum |
Add letter positions → take unit/last digit |
CAT (3+1+20=24) → 24 or 4 |
Number/Symbol Shortcuts
| Letter |
EJOTY |
5-10-15-20-25 |
| Reverse |
VQLGB |
22-17-12-7-2 |
- EJOTY = multiples of 5 → quick pick for middle series.
- VQLGB = reverse of EJOTY → saves 10 s in exam.
3-Step Exam Trick
- Spot: Is it letter/number/symbol?
- Shift: Try ±1, ±2, reverse.
- Verify: Apply to next letter instantly → if matches, rule found.
Common Question Patterns
If TEACHER is coded as VGCEJGT, what is the code for STUDENT?
+2 shift every letter → UVWFMGPIn a certain code, 3456 is coded as 4567. How is 2789 coded?
+1 to every digit → 3890FRAME is coded as IUDPH. What is the code for HOUSE?
+3, +2, +3, +2, +3 → KXWVG
Quick Facts Table (Last-Day Glance)
| Operation |
Key Value |
Memory Hook |
| A→Z |
1→26 |
“AZ” bike (1-26) |
| Middle letter |
13th = M |
“Middle-M” |
| Sum 27 pair |
A-Z, B-Y… |
“27=AB-zy” |
| Fast +5 jump |
E→J→O→T→Y |
“EJOTY” smile |
| Fast -5 jump |
V→Q→L→G→B |
“VQLGB” reverse smile |
One-Liner Mnemonics
- “EJOTY” → every 5th letter → locate in 5 s.
- “VQLGB” → reverse EJOTY → decode in 5 s.
- “Spot-Shift-Verify” → saves 30 s per question.
Golden Last-Day Tip
Spend only 20 s per coding-decoding question in CBT; if stuck, mark Review and move on—85 % accuracy with 20 s beats 100 % accuracy with 60 s.
BETA
