Coding-Decoding

1. What is Coding-Decoding?

Coding-Decoding is a method of encrypting and decrypting words, numbers, or patterns based on specific rules. It tests your analytical and logical reasoning skills.

Encrypting & Decrypting Patterns

Tests Analytical Skills

Based on Specific Rules

Logical Reasoning Application

Simple Definition: Coding is the process of converting words/numbers into codes, while decoding is the reverse process of finding the original message from codes.

Types of Coding-Decoding

Common Coding Patterns

Type	Description	Example
Letter Coding	Letters are coded based on position	A=1, B=2, C=3 or A=Z, B=Y, C=X
Number Coding	Words coded as numbers	CAT = 3-1-20
Substitution	One word substituted for another	RED = APPLE, BLUE = SKY
Mixed Coding	Combination of letters & numbers	A1, B2, C3 pattern
Symbol Coding	Symbols represent letters/words	@=A, #=B, $=C
Pattern Coding	Based on mathematical operations	A+1=B, B+2=D, C+3=F

2. Alphabet Position Values

Memorize these alphabet position values - they are fundamental to coding problems:

A

1

B

2

C

3

D

4

E

5

F

6

G

7

H

8

I

9

J

10

K

11

L

12

M

13

N

14

O

15

P

16

Q

17

R

18

S

19

T

20

U

21

V

22

W

23

X

24

Y

25

Z

26

3. How to Solve Coding-Decoding?

Follow these step-by-step methods to solve coding-decoding questions:

1

Identify the Pattern

Look for mathematical operations, reverse order, or substitution patterns

2

Check Letter Positions

Use alphabet position values (A=1, B=2, etc.)

3

Test the Pattern

Apply the suspected pattern to given examples

4

Verify & Apply

Confirm the pattern works and apply to required word

4. Solved Examples

Example 1: Letter Position Coding

If CAT is coded as 3-1-20, how is DOG coded?

Step 1: Identify pattern - Using alphabet positions

Step 2: C=3, A=1, T=20 → CAT=3-1-20

Step 3: Apply same to DOG → D=4, O=15, G=7

Answer: 4-15-7

Example 2: Reverse Order Coding

If ZEBRA is coded as ARBEZ, how is TIGER coded?

Step 1: Identify pattern - Reverse the word

Step 2: ZEBRA → reverse → ARBEZ

Step 3: Apply same to TIGER → reverse → REGIT

Answer: REGIT

Example 3: Mathematical Operation Coding

If APPLE is coded as 2, 17, 17, 13, 6 then how is MANGO coded? (A=2, B=3, C=4...)

Step 1: Identify pattern - Position + 1

Step 2: A=1+1=2, P=16+1=17, P=16+1=17, L=12+1=13, E=5+1=6

Step 3: Apply to MANGO → M=13+1=14, A=1+1=2, N=14+1=15, G=7+1=8, O=15+1=16

Answer: 14, 2, 15, 8, 16

5. Common Coding Patterns

Letter-Based Patterns

Forward Sequence

A=1, B=2, C=3... Z=26

Backward Sequence

A=26, B=25, C=24... Z=1

Opposite Letters

A↔Z, B↔Y, C↔X... M↔N

Number-Based Patterns

Addition/Subtraction

A+2=C, B+3=E, etc.

Multiplication

A×2=B, B×2=D, etc.

Position Sum

CAT = 3+1+20=24

6. Quick Recap

Pattern Type	Key Concept	Example
Letter Position	A=1, B=2, C=3...	CAT = 3-1-20
Reverse Order	Word written backwards	CODE → EDOC
Mathematical	+/- operations on positions	A+1=B, B+2=D
Opposite Letters	A↔Z, B↔Y pattern	ABC → ZYX
Number to Word	Numbers represent letters	1-2-3 → A-B-C

7. Delhi Police Exam Tips

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Memorize alphabet positions - A=1 to Z=26

✓

Practice all pattern types - letter, number, symbol coding

✓

Look for simplest pattern first - don't overcomplicate

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Verify with given examples before finalizing answer

✓

Time yourself - aim for 30-45 seconds per question