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SSC CGL Coding Decoding

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This page covers SSC CGL Coding Decoding with complete concept notes, 45 graded practice MCQs, key points and exam-specific tips. Free to study.

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Concept Notes

Coding Decoding— Rules & Concept

1.Core Concept

Read this first — the foundation of the topic

CODING DECODING — COMPLETE GUIDE FOR SSC CGL --- CORE CONCEPT ---

Coding-Decoding tests your ability to find a hidden pattern. A word or number is coded using a fixed rule. You must find the rule and apply it to decode the answer. Think of it like a secret language with a fixed formula. --- KEY RULES / PROPERTIES ---

There are 5 main types of Coding-Decoding questions: 1. Letter Coding — Letters are shifted forward or backward in the alphabet.

2. Number Coding — Letters are replaced by numbers (like A=1, B=2 or A=26, B=25). 3. Mixed Coding — Letters and numbers are mixed together.

4. Symbol Coding — Letters are replaced by symbols. 5. Sentence/Word Coding — A full word is coded and you find the code for another word.

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2.Formula Block

Memorise — at least one formula appears in every paper
Forward Shift: If A is coded as D, the shift is +3. So Z+3 = C (wrap around after Z).
Opposite Letter Formula: Opposite of any letter = 27 - Position of that letter.
Example: Opposite of A (position 1) = 27 - 1 = 26 = Z.
Example: Opposite of C (position 3) = 27 - 3 = 24 = X.
Position Values: A=1, B=2, C=3 ... Z=26. Memorise this chain.
Reverse Alphabet: Z=1, Y=2, X=3 ... A=26. Used in many SSC questions.

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Backward Shift: If D is coded as A, the shift is -3.

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3.Exam Patterns

What examiners ask — read before attempting PYQs
Common patterns

- Shift by a fixed number (like +2 or -3). - Use of opposite letters (A=Z, B=Y, C=X). - Alternating shifts (odd positions +2, even positions -1). - Number coding (A=1 type or A=26 type). - Word sentence coding (3 sentences given, find value of one word). --- SHORTCUT / TRICKS --- TRICK 1 — EJOTY Formula (Most Powerful Shortcut): E=5, J=10, O=15, T=20, Y=25. Use this to quickly find position of any letter without counting from A

Example

What is position of R? R is 3 after O(15), so R = 15+3 = 18

TRICK 2 — Mirror Letter Shortcut

A↔Z, B↔Y, C↔X, D↔W, E↔V, F↔U, G↔T, H↔S, I↔R, J↔Q, K↔P, L↔O, M↔N. Any pair adds up to 27. If you see a coding pattern where sum = 27, it is mirror coding

TRICK 3 — Check FIRST and LAST letter only

In many exam questions, checking just the first letter code is enough to eliminate 2-3 wrong options instantly. Save time — don't decode the full word first. ---

4.Worked Example

Solve this step-by-step before moving on
1
Step 1

Find position values. C=3, A=1, T=20 → Sum = 3+1+20 = 24. Correct! D=4, O=15, G=7 → Sum = 4+15+7 = 26. Correct!

2
Step 2

Apply same rule to RAT. R=18, A=1, T=20 → Sum = 18+1+20 = 39. Answer: RAT = 39. --- WORKED EXAMPLE 2 --- Question: If BIND is coded as DKPF, then MIND is coded as?

1
Step 1

Find the shift. B → D: B is position 2, D is position 4. Shift = +2. I → K: I is position 9, K is position 11. Shift = +2. N → P: N is position 14, P is position 16. Shift = +2. D → F: D is position 4, F is position 6. Shift = +2.

2
Step 2

The rule is +2 shift for every letter.

3
Step 3

Apply to MIND. M(13)+2 = O(15), I(9)+2 = K(11), N(14)+2 = P(16), D(4)+2 = F(6). Answer: MIND = OKPF. ---

5.Exam Traps

Common mistakes students make — avoid these

(THE #1 TRAP) --- Students assume the shift is always +1 or +2. In many SSC questions, odd positions and even positions have DIFFERENT shifts. Always check ALL letters before deciding the rule.

Never assume from just one or two letters. This trap appears in nearly 30% of SSC Coding questions.

Key Points to Remember

  • Coding-Decoding finds a fixed rule that converts one word/number into another coded form.
  • EJOTY Formula: E=5, J=10, O=15, T=20, Y=25 — use this to find letter positions instantly.
  • Mirror Letter Rule: Every pair adds to 27. A=Z, B=Y, C=X... M=N. Pair sum is always 27.
  • Forward shift means letters move toward Z; Backward shift means letters move toward A.
  • In Number Coding, A=1 to Z=26 is the most common system used in SSC exams.
  • Reverse Alphabet coding uses Z=1, Y=2, X=3... A=26 — a very common SSC trap variant.
  • Shortcut: Check only the first letter code to eliminate wrong answer options quickly.
  • In Sentence Coding, compare 2-3 coded sentences to isolate the code for one specific word.
  • Always verify the rule on ALL letters in the word, not just the first two.
  • Opposite letter formula: Position of opposite letter = 27 minus position of given letter.

Exam-Specific Tips

  • EJOTY stands for E=5, J=10, O=15, T=20, Y=25 — the fastest position-finding tool in alphabet coding.
  • In mirror/opposite coding, every letter pair (A-Z, B-Y, C-X) sums to exactly 27.
  • SSC CGL typically asks 3 to 5 questions from Coding-Decoding in the Reasoning section every year.
  • In reverse alphabet coding: A=26, B=25, C=24... Z=1. This is the exact reverse of standard A=1 coding.
  • The 5 types of Coding-Decoding tested in SSC are: Letter, Number, Mixed, Symbol, and Sentence coding.
  • In alternating shift coding, odd-position letters and even-position letters follow different shift rules.
  • Position of R in the alphabet = 18. Calculated using EJOTY: O=15, then count 3 more = 18.
Practice MCQs

Coding Decoding — Practice Questions

45graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 45

All MCQs →
Practice 1easy

In a code language, consonants are replaced by the next consonant (B→C, C→D, D→F, F→G, G→H, H→J, J→K, K→L, L→M, M→N, N→P, P→Q, Q→R, R→S, S→T, T→V, V→W, W→X, X→Y, Y→Z, Z→B), and vowels remain unchanged. What is the code for 'SMILE'?

Practice 2easy

In a code, the word 'BOOK' is written as '2-15-15-11'. Each letter is replaced by its position number in the English alphabet (A=1, B=2, C=3, ... Z=26). Using this rule, how is the word 'CARE' coded?

Practice 3easy

In a certain code, vowels (A, E, I, O, U) are replaced by the next vowel in sequence (A→E, E→I, I→O, O→U, U→A), and consonants remain unchanged. For example, 'BAT' becomes 'BET'. Using this rule, what is the code for 'AUDIO'?

Practice 4easy

In a code, consonants are numbered by their position in the English alphabet, and vowels are represented by symbols: A=@, E=#, I=$, O=%, U=&. What is the code for 'SYSTEM'?

Practice 5easy

In a code language, the position of letters in a word is reversed, and then each letter is replaced by the letter 2 positions before it in the alphabet (B→Z, C→A, D→B, etc., wrapping around). What is the code for 'PLAY'?

Practice 6easy

In a code, consonants are coded as the next consonant (B→C, C→D, D→F, F→G, etc., skipping vowels), and vowels are coded as the previous vowel (E→A, I→E, O→I, U→O, A→U). What is the code for 'FRIEND'?

Practice 7easy

In a code, each letter is replaced by the letter that comes 2 positions before it in the English alphabet. For example, C → A, D → B, and so on. Letters A and B wrap around to Y and Z respectively. Using this rule, what is the code for the word 'FRIEND'?

Practice 8easy

In a certain code, each letter is replaced by the letter that comes 3 positions after it in the English alphabet. For example, A is coded as D, B is coded as E, and so on. If the word 'HELLO' is coded using this rule, what is the code?

Practice 9easy

In a certain code, vowels are replaced by the next vowel in sequence (A→E, E→I, I→O, O→U, U→A), and consonants remain unchanged. What is the code for 'MAKE'?

Practice 10easy

In a code, each letter is replaced by the letter that comes 2 positions before it in the English alphabet (B→Z wraps around). For example, C is coded as A. What is the code for 'FRIEND'?

Practice 11easy

In a certain coding system, each letter is replaced by the letter that comes 3 positions after it in the English alphabet. For example, A is coded as D, B is coded as E, and so on. If the word HELLO is coded using this system, what will be the code? Note: After Z, the sequence wraps around to A (i.e., X→A, Y→B, Z→C).

Practice 12easy

In a certain code, each letter is replaced by the letter that comes 3 positions after it in the English alphabet. For example, A is coded as D, B is coded as E, and so on. If the word 'HELLO' is coded using this rule, what is the code?

Practice 13easy

In a certain coding system, each letter is replaced by the letter that comes 3 positions ahead of it in the English alphabet. For example, A is coded as D, B is coded as E, and so on. If a letter reaches beyond Z, it wraps around to the beginning (so X→A, Y→B, Z→C). Using this rule, how would the word 'PLAY' be coded?

Practice 14easy

In a certain code, each letter is replaced by the letter that comes 3 positions after it in the English alphabet. For example, A is coded as D, B is coded as E, and so on. If the word 'HELLO' is coded using this rule, what is the coded word?

Practice 15easy

In a code language, vowels are replaced by the next vowel in sequence (A→E, E→I, I→O, O→U, U→A), and consonants remain unchanged. What is the code for the word 'BRAIN'?

Practice 16easy

In a code, each letter is replaced by a number: A=1, B=2, C=3, ..., Z=26. If 'CAT' is coded as 3-1-20, what is the code for 'DOG'?

Practice 17easy

In a certain code, the first and last letters of a word are swapped, and all other letters remain in their original positions. For example, 'BOOK' becomes 'KBOO'. What is the code for 'PENCIL'?

Practice 18easy

In a code language, vowels (A, E, I, O, U) are replaced by the next vowel in sequence (A→E, E→I, I→O, O→U, U→A), and consonants remain unchanged. Using this rule, what is the code for 'BRAIN'?

Practice 19easy

In a certain code, each letter is replaced by a number: A=1, B=2, C=3, ..., Z=26. If 'CAT' is coded as 3-1-20, what is the code for 'DOG'?

Practice 20easy

In a certain code language, each letter is replaced by the letter that comes 3 places after it in the English alphabet (A=D, B=E, C=F, ...). Using this rule, what is the code for the word 'COLD'?

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60-Second Revision — Coding Decoding

  • Remember: EJOTY = E(5), J(10), O(15), T(20), Y(25) — find any letter position in 2 seconds.
  • Formula: Opposite letter position = 27 - position of given letter. Pair always sums to 27.
  • Trick: Check only the first letter of the coded word to eliminate wrong options fast.
  • Trap: Do NOT assume a uniform shift from just 1-2 letters — always check all letters. Alternating shifts are a common SSC trick.
  • Remember: Reverse alphabet coding uses A=26 to Z=1, which is opposite of the standard A=1 system.
  • For Sentence Coding: compare coded sentences side by side and find the common word to isolate its code.
  • Formula: Forward wrap-around — after Z comes A again. If Z+2 = B (position 26+2=28, 28-26=2=B).
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