Coding-Decoding Questions for SSC CGL

Alphabet Position Basics

Every letter has a fixed position A=1, B=2 ... Z=26. Most coding rules involve adding, subtracting, or reversing these positions. A parallel reverse series exists: A=26, B=25 ... Z=1, called the Reverse Alphabet Position. Knowing both series by heart saves 20-30 seconds per question.

• Forward: A=1, B=2, C=3 ... M=13, N=14 ... Z=26
• Reverse: A=26, B=25, C=24 ... Z=1
• EJOTY trick: E=5, J=10, O=15, T=20, Y=25. Use these anchors to find any letter quickly.
• Opposite letter pairs: A-Z, B-Y, C-X, D-W, E-V ... (sum always = 27)
• Middle of alphabet: M=13 and N=14

Letter Coding (Word to Word)

A word is given with its code. You find the rule — each letter shifts by a fixed number forward or backward in the alphabet, or is replaced by its opposite. Apply the same rule to the new word. Always check: is the shift the same for every letter? Is it the opposite letter? Is every letter moved +2, -3, etc.?

• Check if each letter shifts by the same fixed number (e.g. +2 means A becomes C)
• Check if each letter is replaced by its reverse/opposite (A-Z pair)
• Check if the word is written in reverse order first, then shifted
• Common shifts in PYQs: +1, +2, +3, -1, -2, -3
• Sometimes alternate letters shift differently — check even and odd positions separately

Number Coding

Letters are replaced by numbers using some rule. Common rules: position number directly (A=1), position+some constant, reverse position (A=26), or product/sum of position digits. In some questions, a full word is given one code number — then the number is the sum, product, or some operation on all letter positions.

• Single letter to number: usually position, reverse position, or position +/- constant
• Whole word to one number: usually sum of letter positions or sum of digits of positions
• Check if the code number matches sum of letter positions first — that is most common
• If sum does not match, try: sum of (position values squared), product, or digit sum of positions
• In mixed number-symbol coding, treat each symbol as a placeholder and focus on the number pattern

Conditional or Substitution Coding

A set of conditions is given: if the first letter is a vowel do X, if the last letter is a consonant do Y, etc. These questions look scary but follow a simple if-then logic. Read all conditions first, identify which condition applies to the given word, then apply only that rule. Do not mix rules.

• Read ALL conditions before picking one — a common trap is applying the wrong condition
• Conditions are usually based on: vowel/consonant, capital/lowercase, odd/even position
• Only ONE condition typically applies per question — they are mutually exclusive
• If no condition matches, use the default (base) code given in the table
• These appear more in Tier 2 and sectional tests — practice 5-6 PYQs of this type

Symbol and Mixed Coding

Words are coded using symbols, or a mix of numbers and symbols. The approach is the same: look at multiple coded statements and find the common word that appears in two statements — its code appears in both. By elimination, you can decode individual words. This is the trickiest type and requires 2-3 statements.

• Use two statements with one common word to identify that word's code
• Use three statements to isolate codes of individual words by elimination
• Write each word and its possible codes in a table format on rough paper
• This type rewards systematic working — do not try to guess
• If only one statement is given with options, test each option against the visible pattern

• Assuming the shift is always +1 without verifying all letters — always check every letter in the sample pair before applying the rule.
• Confusing forward position (A=1) with reverse position (A=26) — whenever the code letter seems unrelated, try the reverse series.
• In substitution coding, applying multiple conditions when only one should apply — read the conditions as if-else, not if-and.
• Forgetting that the word order can be reversed before shifting — if the rule does not work letter by letter, try reversing the word first.
• In number coding, stopping at the sum rule when the match fails — move to product or digit-sum of positions systematically instead of guessing.

• EJOTY anchor: E=5, J=10, O=15, T=20, Y=25. Memorise this like a phone keypad. Any letter near these is easy to find in seconds.
• Opposite pairs sum to 27: Think of it as A+Z = 1+26 = 27. So opposite of any letter = 27 minus its position. Call it the 27 Rule.
• 3-step attack for any coding question: Step 1 Find the rule on the given pair. Step 2 Verify with all letters. Step 3 Apply to new word. Never skip Step 2.
• For symbol coding, draw a mini table: rows = statements, columns = words. Circle repeats. This visual grid breaks the problem in 30 seconds.

• SSC CGL Tier 1 usually has 2-3 coding-decoding questions. Tier 2 (Paper 1 Reasoning section) can have 4-5. Budget 30-40 seconds per question — these should be quick scorers.
• Letter-shift coding (+1, +2, -1, -2) is the single most common type in recent PYQs (2019-2024). Practise spotting the shift in under 10 seconds.
• The reverse-alphabet (opposite letter) coding appeared in 3 out of 5 recent SSC CGL papers — always try the 27-rule if the direct shift does not work.
• Substitution and symbol coding appear more in Tier 2 and are slightly tougher. If stuck, use the elimination table method on rough paper rather than trying to solve mentally.
• Never leave a coding question blank — if the rule is unclear, eliminate options by checking just one letter of the answer against the pattern. Even partial pattern matching narrows choices to 1-2 options.