Coding-Decoding Reasoning Questions with Answers – Practice Set 2026

Coding-Decoding is an important topic in the Reasoning section of many competitive examinations. Questions are based on a simple rule used to replace letters, numbers or words with a different code. This practice set will help you understand common coding patterns and improve your problem-solving speed.

In this article: Letter Coding, Reverse Alphabet Coding, Number Coding, Word Coding, Solved Examples and an Interactive Practice Quiz.

1. What Is Coding-Decoding?

Coding-Decoding is a reasoning technique in which a word, letter or number is changed according to a specific rule. Your task is to identify the rule and apply it to another word or letter.

For example, if CAT is written as DBU, each letter has been moved one position forward in the English alphabet:

C → D   A → B   T → U

Therefore, CAT → DBU

2. Important Coding-Decoding Rules

Rule 1: Forward Letter Coding

Each letter is moved forward by a fixed number of positions.

Example: BOOK → CPPL, because every letter moves one position forward.

Rule 2: Backward Letter Coding

Each letter is moved backward by a fixed number of positions.

Example: DBU → CAT, because every letter moves one position backward.

Rule 3: Reverse Alphabet Coding

Each letter is replaced by its opposite letter in the alphabet: A ↔ Z, B ↔ Y, C ↔ X, and so on.

Example: CAT → XZG.

Rule 4: Letter Position Values

Every letter has a position value: A = 1, B = 2, C = 3 ... Z = 26.

Example: DOG = 4, 15, 7.

Rule 5: Identify the Pattern First

Check whether the letters move forward or backward, whether their order is reversed, or whether a number or symbol pattern is being used. Do not assume a rule before checking all the given letters.

3. Solved Examples

Question 1: If PEN is coded as QFO, how will CAT be coded?

Solution: Each letter moves one position forward. C → D, A → B, T → U.

Answer: DBU

Question 2: If A = 1, B = 2, C = 3, what is the value of BAD?

Solution: B = 2, A = 1 and D = 4.

Answer: 2, 1, 4

Question 3: In reverse alphabet coding, how is DOG coded?

Solution: D → W, O → L, G → T.

Answer: WLT

4. Coding-Decoding Practice Quiz

Attempt all 10 questions without checking the answers first. Select one option for each question and click Submit Quiz to see your score.

Q1. If CAT is coded as DBU, how is DOG coded? ENH EPH FPH EOG

Q2. If BOOK is coded as CPPL, how is PEN coded? ODM QFO QFO RGP

Q3. If A = 1, B = 2, C = 3, what is the value of BAD? 2, 1, 4 1, 2, 4 2, 4, 1 4, 1, 2

Q4. In reverse alphabet coding, CAT becomes: DBU XZG GZX XZG

Q5. If SUN is coded as TVO, how is MOON coded? NPPM NPPO NQPO MPPO

Q6. If each letter moves two positions forward, CAT becomes: DBU ECV ECV FCW

Q7. What is the position value of M in the English alphabet? 13 12 14 15

Q8. If RAM is coded as SBN, how is BAT coded? AZS CBU DBU CBU

Q9. If the alphabet is written backward, which letter replaces B? X Y Z W

Q10. If ACE is coded by moving each letter one position forward, the result is: BDF ZBD BDF CEG

5. Answer Key with Explanations

1. EPH: D → E, O → P, G → H.
2. QFO: P → Q, E → F, N → O.
3. 2, 1, 4: B = 2, A = 1, D = 4.
4. XZG: C ↔ X, A ↔ Z, T ↔ G.
5. NPPO: M → N, O → P, O → P, N → O.
6. ECV: C → E, A → C, T → V.
7. 13: M is the 13th letter.
8. CBU: B → C, A → B, T → U.
9. Y: B is paired with Y in reverse alphabet coding.
10. BDF: A → B, C → D, E → F.

6. Preparation Tips

• Memorise alphabet positions from A = 1 to Z = 26.
• Practise forward and backward letter movements.
• Learn reverse alphabet pairs such as A-Z, B-Y, C-X and D-W.
• Check every letter carefully before selecting an option.
• Use a timer when practising to improve speed without sacrificing accuracy.
• Review incorrect answers and identify the rule you missed.

Frequently Asked Questions

Is Coding-Decoding important for competitive exams?

It is a common reasoning topic in many competitive-exam syllabuses. The exact number and type of questions depend on the examination.

How can I improve my Coding-Decoding speed?

Practise alphabet positions, reverse-letter pairs and different coding patterns regularly. Review mistakes instead of memorising answers.

Can beginners attempt this practice set?

Yes. The examples begin with simple letter shifts and progress to mixed practice questions.

Conclusion

Coding-Decoding becomes easier when you identify the pattern instead of guessing the answer. Learn the basic rules, practise the questions and check your mistakes using the answer key. Attempt the quiz again to improve your accuracy.

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