# Coding-Decoding — Letter Shifts, Reverse Codes and Number Codes

Source: https://skills101.in/learn/reasoning/coding-decoding — Skills101 free tutorial (Logical Reasoning). Updated 2026-11-09.

In coding-decoding, a word is written in a secret way. You find the rule from one example, then apply it to another word.

## 1. Letter shift codes

![COLD becomes DPME: every letter moves forward by 1](https://skills101.in/learn-img/reasoning/coding-shift.svg)

### Example 1
*If COLD is written as DPME, how is WARM written?*

Each letter moves +1: W→X, A→B, R→S, M→N → **XBSN**.

### Example 2 — changing shifts
*If PLANT is coded as QNDRY, how is GREEN coded?*

P→Q (+1), L→N (+2), A→D (+3), N→R (+4), T→Y (+5). Apply to GREEN: G+1 = H, R+2 = T, E+3 = H, E+4 = I, N+5 = S → **HTHIS**.

> Always write the **positions** of both words in two rows and subtract. The rule appears immediately.

![Alphabet with positions 1 to 26, EJOTY highlighted; opposite letters add to 27](https://skills101.in/learn-img/reasoning/alphabet-positions.svg)

## 2. Opposite (reverse) letter codes

The opposite of a letter is the letter at the same distance from the other end: A↔Z, B↔Y, C↔X … **positions add up to 27**.

### Example 3
*If GOLD is coded as TLOW, how is SILVER coded?*

G(7)→T(20): 7 + 20 = 27 ✓ — opposite letters. SILVER → S↔H, I↔R, L↔O, V↔E, E↔V, R↔I → **HROEVI**.

## 3. Reversing the word

### Example 4
*If BRAIN is coded as NIARB, how is HEART coded?* → written backwards → **TRAEH**.

Sometimes the word is reversed **and** shifted. Check both.

## 4. Number codes

### Example 5
*If CAT = 24 (3 + 1 + 20), what is DOG?*

D(4) + O(15) + G(7) = **26**.

### Example 6
*If BAD is written as 214, how is FACE written?* → positions → **6135**.

## 5. Sentence (word) codes

Several sentences are coded word by word. Find the word that appears in two sentences — its code is the code that appears in both.

### Example 7
*"sky is blue" → "ta na ri"; "blue is nice" → "ri po ta". What is the code for "nice"?*

"is" and "blue" are common to both sentences, and "ta" and "ri" are common codes. So "nice" = the remaining code of the second sentence = **po**. (And "sky" = na.)

## Common mistakes

- Counting letters on fingers — use positions and EJOTY.
- Forgetting to "wrap around": after Z comes A again (Y + 3 = B).
- In sentence codes, assuming the order of words matches the order of codes. It usually does **not**.

## Quick recap

- Write positions of the word and its code; subtract to find the rule.
- Opposite letters add to 27.
- Check reversing, shifting and both.
- Sentence codes: match common words with common codes.


Practice quiz and free certificate: https://skills101.in/learn/reasoning/coding-decoding