Coding‑Decoding – Study Notes (Navy SSR – Reasoning Ability)
1. Simple Explanation
Coding‑decoding is a type of verbal reasoning problem that asks you to find the relationship between a word (or set of words) and a series of numbers (or another set of words).
Once you discover the rule, you can decode any other word or encode a new word.
Typical formats
| Format | What you’re given | What you must produce |
|---|---|---|
| A → B | One word A and a set of numbers B | The coded numbers for a new word |
| A → B, C → D | Two word‑number pairs | Find D for a new word C |
| X → Y format | Word X is represented by Y (often numbers) | Find Y for a new X |
The key is spotting patterns: letter positions, sums, differences, alphabetical positions, repetition, symmetry, etc.
2. Key Points & Common Patterns
| Pattern | How to spot it | Example (Word → Numbers) | Why it works |
|---|---|---|---|
| Alphabetic value (A=1, B=2, … Z=26) | Sum or individual values of letters | APPLE = 1+16+16+12+5 = 50 → 50 |
Simple arithmetic |
| First/Last letter value | Only the first/last letter is used | BIRD = 2 (B) |
Quick shortcut |
| Number of letters | Word length → single digit | CAT = 3 |
Very common in short questions |
| Letter frequency | Count repeated letters | BOOK = B(1), O(2), K(1) → 1 2 1 |
Shows emphasis on repeats |
| Position‑based | Position of a specific letter in alphabet | DOG = 4 (D) + 15 (O) + 7 (G) = 26 |
Adds depth |
| Alternating pattern | Alternate adding/subtracting letter values | HAPPY = (8‑1+16‑16+25) = 32 |
Requires careful tracking |
| Sum of positions of vowels/consonants | Separate vowels & consonants | MUSIC = (M+U+C+I+S) = 13+21+3+9+19 = 65 |
Vowel‑consonant split |
| Mirror/Reverse | Reverse the word before encoding | STOP → POTS → 16 15 20 19 |
Tests recognition of reversal |
| Word length × letter value | Multiply word length by a letter value | TREE (4 letters) × R(18) = 72 |
Combination of two ideas |
| Difference between successive letters | Subtract successive alphabetic values | FISH: (6-9)=-3, (9-19)=-10, (19-8)=11 → -3 -10 11 |
Often yields negative numbers |
| Pattern in the given coding | Observe if numbers are increasing, decreasing, or repeating | ABCD = 1 2 3 4 |
Simple sequential pattern |
Tip: Always write down the alphabetic values of each letter first; it reveals many hidden patterns.
3. Worked Example
Problem (typical of Navy SSR):
| Word | Code |
|---|---|
| MOTOR | 13 15 20 15 18 |
| POWER | 16 15 23 5 18 |
Find the code for:
GUN
Step‑by‑Step Solution
-
Write alphabetic values
Word Values MOTOR 13 15 20 15 18 POWER 16 15 23 5 18 -
Look for a pattern
- Notice that the code for each letter is exactly the alphabetic value of that letter.
- Example:
- M → 13
- O → 15
- T → 20
- U → 21 (if it appeared)
- R → 18
The codes match the values directly.
-
Apply the rule to GUN
Letter Alphabetic value Code G 7 7 U 21 21 N 14 14 -
Result
GUN → 7 21 14
Alternate Quick Check
If you had suspected a sum pattern, you’d sum the values:
- MOTOR = 13+15+20+15+18 = 81 → But the code shows the individual values, not the sum.
- POWER = 16+15+23+5+18 = 77 → Again, the code lists individual values.
So the rule is letter → its alphabetic value.
4. Quick Revision Summary
| What to remember | How to apply it |
|---|---|
| Alphabetic value | Write A=1…Z=26; often used directly. |
| Word length | Short codes (single digit) often equal length. |
| Letter frequency | Codes may reflect how many times a letter appears. |
| First/Last letter | Some codes use only the first or last letter’s value. |
| Positional pattern | Add/subtract successive letters, or use position in word. |
| Mirror/reverse | Reverse the word before coding if pattern shows reversed order. |
| Check for sums | Sum of all letters or of vowels vs consonants. |
| Always test multiple patterns | Try a few before committing. |
| Keep a cheat sheet | Quick |