📚 Coding‑Decoding for Andaman & Nicobar PSC
(Reasoning Ability – Beginner’s Guide)
1️⃣ What Is Coding‑Decoding?
- Coding = finding a hidden rule.
- Decoding = using that rule to predict missing items or find the answer.
- Think of it as a secret recipe that you must guess and then use to cook a new dish.
2️⃣ Everyday Analogy
Imagine a friend writes a note:
“The first letter of each word becomes a number: A=1, B=2 …”
You read the note, figure out the rule, and then can write your own note following the same rule.
That’s exactly what coding‑decoding does – you discover the rule, then apply it.
3️⃣ How to Solve a Coding‑Decoding Question
| Step | What to Do | Quick Tip |
|---|---|---|
| 1. Look for patterns | Check letters, numbers, shapes, or positions. | Compare the first two items – how are they different? |
| 2. Identify the rule | Write down the change from item 1 to item 2. | Use one letter or number at a time. |
| 3. Test the rule | Apply it to the next item in the series. | If it works, you probably found the rule. |
| 4. Decode the unknown | Use the rule to find the missing or next item. | If the answer is a letter, write it; if a number, write the number. |
| 5. Double‑check | Make sure the rule works for every given pair. | If something breaks, go back and re‑examine. |
4️⃣ Common Coding‑Decoding Patterns
| Pattern | Example | How to Spot It |
|---|---|---|
| Alphabet shift | A → C, B → D, … | Next letter moves forward by the same amount. |
| Number reversal | 12 → 21 | Digits are flipped. |
| Alternating addition/subtraction | 1, 3, 5, 7 | Add 2 each time. |
| Position in the alphabet | A(1), B(2), C(3) | Letter value equals its position. |
| Shape similarity | Circle → Oval → Oval → Circle | Look at the shape, not the number. |
| Mirror image | 8 → 8, 6 → 9 | Numbers that look the same upside‑down. |
5️⃣ Tiny Example
Series:
A 1
B 2
C 3
? ?
Step 1 – Pattern?
- Letters go A, B, C (next would be D).
- Numbers go 1, 2, 3 (next would be 4).
Answer:
D 4
No tricks, just a simple match of position.
6️⃣ Quick Practice Problem
Series
1 A
2 C
3 E
4 ?
Find the missing pair.
| Step | Explanation |
|---|---|
| 1. Look at numbers | 1, 2, 3, 4 → increase by 1. |
| 2. Look at letters | A, C, E → skip one letter each time (B, D). |
| 3. Apply to 4 | Next letter after E skipping one is G. |
| Answer | 4 G |
7️⃣ Tips for the PSC Exam
- Practice daily – 10‑15 coding‑decoding problems a day.
- Keep a cheat‑sheet – write down common patterns you see.
- Time yourself – aim to finish each problem in 1–2 minutes.
- Check your work – always verify the rule works for all given pairs.
- Stay calm – the rule is always simple; you just need to see it.
8️⃣ Quick Self‑Quiz
| Question | Answer |
|---|---|
If the series is X 24, Y 25, Z 26, what comes next? |
AA 27 (letters wrap to double letters; numbers continue) |
Series: 2 B, 4 D, 8 F, ? |
16 H (double the number, skip one letter) |
Series: 1 A, 4 D, 9 I, ? |
16 P (square numbers, skip letters) |
Try solving them on your own before checking the answers!
🎯 Final Thought
Coding‑decoding is just a puzzle that asks you to find a secret rule and then use it. Treat it like a simple recipe: discover the ingredients, mix them, and you’re ready to cook the answer!