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SSC CGL Reasoning · Coding-Decoding

Letter Shifts

Each letter of the word moves a fixed number of places along the alphabet: one shift for every letter, a pattern of shifts that changes from letter to letter, or one shift for vowels and another for consonants.

All Coding-Decoding notes

Why this matters

Eighty-two questions in the bank, fifty-two of them from the 2025 shifts and sixty-three EASY. Forty-four move every letter by the same amount, and the wrong options usually differ from the answer in a single letter, so the marks go to the student who knows the alphabet positions cold and checks the letter where the options split.

Concept 1 of 3: One shift for every letter

Put the word above its code and count how far the first letter moved. If the second and third letters moved the same distance, the whole code is that one shift, and you can write the answer without thinking about the rest.

Definition

  • Positions: A = 1, B = 2, and so on to Z = 26. Learn the anchors EJOTY: E = 5, J = 10, O = 15, T = 20, Y = 25. Every other letter is a short count from one of them: R is two before T, so 18.
  • Find the shift: count from a word letter to its code letter, forward (+) or back. Check the same count on two more letters before you trust it.
  • Wrap round: going forward past Z starts again at A (Y + 3 = B); going back past A starts again at Z (B back 3 = Y). In numbers, take away 26 when you pass 26, add 26 when you go below 1.
  • Coding the code: 'If MASTER is NBTUFS, how is NBTUFS coded?' means apply the same shift once more to NBTUFS. The answer is two shifts away from MASTER.
  • Decoding: if the code is given and the word is asked, move the code letters the other way.
  • Fast route: write only the first two letters of the answer and strike out the options that differ. If two options are left, go to the first letter where they differ and work out only that one.

Moving a letter k places forward

new position=p+k(take away 26 if the total is above 26)\text{new position} = p + k \quad (\text{take away } 26 \text{ if the total is above } 26)
  • ppthe position of the letter in the word (A = 1, Z = 26)
  • kkthe shift; for a shift back, use a minus sign

Worked example

In a certain code language, 'WORLD' is written as 'ZRUOG'. How will 'YACHT' be written in that language?
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2025 · Tier I, 23 Sep 2025, Shift 3 · Q11Easy

Example 1 · Coding-Decoding · Letter Shifts

If "EUROPE" is coded as "AQNKLA", how is "RUSSIA" coded?

Forgetting to wrap round

Moving forward past Z carries on from A, and moving back past A carries on from Z: A moved 3 places back is X. An option that stops at Z or A, or prints a letter that ignores the wrap, is a printed trap.

Answering with the first code when the code is coded again

'If CROWN is DSPXO, how is DSPXO coded?' asks for the shift applied to DSPXO itself. The answer, ETQYP, is two shifts away from CROWN; giving DSPXO back loses the mark.

Checking only the first letter

The four options usually share their first two or three letters. Compare them first and work out the letter where they split, instead of the letters they all agree on.
Drill 43 more on one shift for every letter

Concept 2 of 3: A pattern of shifts that changes from letter to letter

When the first two letters moved by different amounts, write the gap under every letter. The row of gaps is the rule: it alternates, it grows, it shrinks, or it simply belongs to each position, and the new word takes the same row of gaps.

Definition

1. Write the word, its code under it, and the gap under each pair: +2, +3, +2, +3 or +1, back 1, +1, back 1. 2. Read the row of gaps. The common shapes are alternating (+1, back 1, +1, back 1), growing (+1, +2, +3, ...), shrinking (+4, +3, +2, +1), a block that repeats (+1, back 2, 0, then again), or two halves with different gaps. 3. If no shape shows, use the gaps as they stand, position by position: the third letter of the new word gets the third gap. With only one example this is always safe, because it is exactly what the example shows. 4. If a second example is printed, check the row of gaps on it too. 5. Fast route: the gaps of the first two letters already strike out most options. Work the rest of the word only if two options survive.

Worked example

In a certain code language, 'FOREST' is written as 'GMSCTR'. How will 'BRIDGE' be written in that language?
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2025 · Tier I, 26 Sep 2025, Shift 3 · Q24Moderate

Example 2 · Coding-Decoding · Letter Shifts

If FRIEND is coded as HUMJTK, how is CANDLE written in that code?

Taking the first gap as the rule for every letter

A code can start +2, +2 and still move the third letter by +3. Write the gap under every letter of the example before you apply anything to the new word.

Turning a backward gap into a forward one

O to M is 2 places back. Written as +2 it sends the new word's letter the wrong way, and SSC prints that letter as an option. Mark each gap with its direction.

Forcing a shape that is not there

Gaps such as +1, back 1, +1, +1, +2 make no neat shape, and they do not need to. Use them position by position; inventing a 'next term' for a pattern you guessed is how the wrong option gets chosen.
Drill 31 more on a pattern of shifts that changes from letter to letter

Concept 3 of 3: Vowels and consonants moved differently

If some letters of the code are the same as the word and others have moved, look at which letters stayed. When they are the vowels, the rule has two parts: one for vowels, one for consonants.

Definition

  • The vowels are A, E, I, O, U; every other letter is a consonant.
  • Usual rules: vowels stay and consonants move; consonants stay and vowels move; or vowels move by one amount and consonants by another.
  • Decide the rule by the letter in the word, never by the letter it becomes: E moved 1 forward becomes F, a consonant, but it was moved as a vowel.
  • Fast route: find a vowel in the new word and see what each option does with it. That one letter usually leaves a single option.

Worked example

In a certain code language, 'PLANET' is written as 'QMAOEU'. How will 'MOTHER' be written in that language?
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2024 · Tier I, 13 Sep 2024, Shift 1 · Q10Easy

Example 3 · Coding-Decoding · Letter Shifts

In a certain code language, ‘HUSBAND’ is written as ‘JVUDBPF’ and ‘SISTER’ is written as ‘UJUVFT’. How will ‘BROTHER’ be written in that language?

Judging the letter after it has moved

A vowel moved 1 forward can turn into a consonant (E to F, O to P). The rule is fixed by what the letter was in the word, so do not move it a second time as a consonant.

Calling it one shift when the vowels stayed

If 'every letter +1' fits the consonants but not the vowels, the rule is not wrong at one letter: the vowels follow a rule of their own. Check every vowel of the example.
Drill 5 more on vowels and consonants moved differently

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Formulas (1)

  • One shift for every letter

    Moving a letter k places forward

    new position=p+k(take away 26 if the total is above 26)\text{new position} = p + k \quad (\text{take away } 26 \text{ if the total is above } 26)

Watch out for (8)

Test yourself on Coding-Decoding

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