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SSC CGL Preparation – Day 6
Reasoning – Coding-Decoding (Basic to Moderate Level)
π What is Coding-Decoding?
In coding-decoding, a word or a number is transformed into a secret code by following a certain rule or logic. The objective is to identify the logic used and apply it to find the answer.
π― Importance in SSC CGL
- 2β3 questions are usually asked in Tier 1
- Frequently asked and easy to score
- Based on pattern recognition and vocabulary/logical analysis
π§© Types of Coding-Decoding Questions
1. Letter Coding
A word is written in code using specific letter substitutions.
Example:
If COLD is coded as DPME, what is the code for WARM?
Solution:
Compare each letter:
C β D (+1), O β P (+1), L β M (+1), D β E (+1)
So, W β X, A β B, R β S, M β N
Answer: XBSN
2. Number Coding
Words are coded using numbers based on alphabetical positions.
Example:
If BAD is coded as 214, what is the code for ACE?
Solution:
A = 1, C = 3, E = 5
Answer = 135
3. Substitution Coding
Words are replaced with unrelated words. Itβs vocabulary-based.
Example:
If βPenβ is called βBookβ, βBookβ is called βPencilβ, βPencilβ is called βEraserβ, then what do we write with?
Answer: βPencilβ is used to write, and itβs called Eraser.
4. Mixed Letter Coding
Codes for 2β3 statements are given. We must deduce the code for a word by comparing statements.
Example:
- βRavi is goodβ β ka la ma
- βHe is badβ β la na da
What is the code for is?
Solution:
Common word = βisβ, common code = la
Answer: la
5. Matrix Coding
A matrix is given with letters arranged in rows and columns. A letter is coded by referring to its position.
Example:
0 | 1 | 2 | |
---|---|---|---|
0 | A | B | C |
1 | D | E | F |
2 | G | H | I |
Code for E = 11
6. Symbol Coding / Conditional Coding
Questions involve interpreting symbolic logic and conditional assignments.
Example:
If β+β means βΓβ, βΓβ means βββ, βββ means βΓ·β, βΓ·β means β+β, then
20 β 5 Γ 2 = ?
Replace:
20 Γ· 5 β 2 = 4 β 2 = 2
7. Decoding Based on Alphabetical Positions
Sometimes questions involve direct manipulation of alphabetic positions (A = 1, B = 2 β¦ Z = 26)
Example:
If HAND is coded as 85144, find the code for FIND.
F = 6, I = 9, N = 14, D = 4
Answer: 69144
π Tips & Tricks
- Memorize Alphabet Positions:
A=1, B=2, …, Z=26
(Reverse: Z=1, Y=2, … A=26 β for reverse coding) - Check Pattern of Shifts:
+1, β2, alternate letters, etc. - Use Elimination in MCQs
Narrow down options based on even one letter decoded. - Compare Similar Words
In sentence coding, compare common words.
π Common Alphabet Positions (for quick recall)
A | E | I | M | Q | U | Y |
---|---|---|---|---|---|---|
1 | 5 | 9 | 13 | 17 | 21 | 25 |
B | F | J | N | R | V | Z |
---|---|---|---|---|---|---|
2 | 6 | 10 | 14 | 18 | 22 | 26 |
π§ͺ Practice this flow:
- Identify type of coding
- Map original & coded word
- Spot consistent logic or rule
- Apply the same rule to new word
- Eliminate options logically