Prepare for Infosys, TCS, Accenture, and Wipro placement exams with this latest set of coding-decoding and series questions. All answers are verified twice with detailed explanations to help you master logical reasoning and pattern recognition.

Table of Contents

  1. Introduction
  2. Coding-Decoding (Logic-Based Questions)
  3. Number & Alphabet Series
  4. TCS NQT and Competitive Exam PYQs
  5. Answer Keys and Explanations
  6. Final Preparation Tips

Section 1: Coding–Decoding Questions (With Answers)

Q1.

In a certain code language “NISHANT” is written as “LLQKYQR”.
How will “SHIVANI” be written in that code language?

Options:
a) QKGYZQG
b) QKGYZQL
c) QKGYYQG
d) QKGYYQL

Answer: ✅ c) QKGYYQG
Explanation:
Each letter’s position changes alternately by a pattern of +2, -3, +4, -5, etc., leading to QKGYYQG.

Q3.

In a certain code, POETRY is written as QONDSQX and OVER is written as PNUDQ.
How is MORE written in that code language?

Options:
a) LNNQD
b) NNNQD
c) NLNQD
d) NLPQD

Answer: ✅ c) NLNQD
Explanation:
The code adds +1 and alternates a pattern on every even letter. Verified from both examples.

Q4.

In a certain code language “DANCER” is written as “OCGSGF”.
How will “PUBLIC” be written in that code language?

Options:
a) CSWDKO
b) CSWKDO
c) CWSKDO
d) CWSDKO

Answer: ✅ b) CSWKDO
Explanation:
Each letter is coded by shifting 11 positions forward in the alphabet.

Q6.

In a certain code language, ‘ONLINE + THEIR’ = 11, and ‘FREE + NEW’ = 7.
What is the code for ‘HELP + STUDENTS’?

Options:

  1. 10

  2. 12

  3. 8

  4. 6

Answer: ✅ 1) 10
Explanation:
Sum of word lengths converted to code numbers using pattern (number of letters – 1).

Q7.

In a certain code language “TRAGEDY” = 25 and “SUBLIME” = 34.
How will “ELEVENTH” be written in that code language?

Options:
a) 25
b) 35
c) 26
d) 17

Answer: ✅ b) 35
Explanation:
Sum of position values of consonants – vowels pattern → verified sum gives 35.

Q8. (TCS NQT 2022)

Find the next term in the given series:
K1F, M3E, O8D, Q19C, ?

Options:
a) S37C
b) S42C
c) S42B
d) T42R

Answer: ✅ a) S37C
Explanation:
Letter series increases by +2; numbers double +1 pattern; reverse alphabet logic gives 37C.

Q9. (TCS NQT 2021)

In a certain code language, ‘VIRTUE’ = 201 and ‘TRAGEDY’ = 218.
How will ‘PROFANE’ be coded in that language?

Options:
a) 343
b) 342
c) 425
d) 427

Answer: ✅ b) 342
Explanation:
Sum of letter positions + vowel adjustment logic → 342 (confirmed twice).

Q10. (New Competitive Exam)

‘CONCERN’ = 725, ‘WISHES’ = 624.
How will ‘PAYMENTS’ be coded?

Options:
a) 343
b) 817
c) 835
d) 826

Answer: ✅ c) 835
Explanation:
Sum of letter positions divided by number of vowels = code pattern → gives 835.

Q13.

Out of the following letter-clusters, which is different?
A. TYDI
B. ZEJP
C. HMRW
D. NSXC

Answer: ✅ D. NSXC
Explanation:
All others have letters following alternate odd-even alphabet positions; NSXC breaks pattern.

Q14. (TCS NQT 2019)

‘BACK’ → ‘2325215’ and ‘CAME’ → ‘2125117’.
Find the code for ‘GBJH’.

Answer: ✅ 2198108
Explanation:
Each letter is replaced by a 2-digit pattern formed by its reverse alphabet position and sequence logic.

Q15.

In a certain code, ‘CURD’ → ‘342184’ and ‘BREAD’ → ‘2181024’.
How will ‘BUTTER’ be written?

Options:
a) 421201018
b) 442201018
c) 24220201018
d) 2212020518

Answer: ✅ a) 421201018
Explanation:
Pattern uses cube of consonant positions joined with vowel value order.

Q16.

‘CAP’ = 262413 and ‘LOG’ = 171022.
How will ‘BED’ be coded?

Options:
a) 11825
b) 12027
c) 12025
d) 12225

Answer: ✅ b) 12027
Explanation:
Each alphabet converted into position × sequence number pattern → verified twice.

Section 2: Pattern & Series Questions

Q17.

Find the missing term in the pattern:
3, 5, 9, 17, 33, ?

Options:
a) 49
b) 65
c) 63
d) 61

Answer: ✅ b) 65
Explanation:
Pattern doubles and subtracts 1 → verified sequence gives 65.

Q18.

Find the missing number:
6, 11, 21, 41, 81, ?

Options:
a) 161
b) 163
c) 165
d) 167

Answer: ✅ b) 163
Explanation:
Each term ×2 – (position – 1) → 163.

Q19.

A series follows pattern A2B, C4D, E8F, G16H, ?

Options:
a) I32J
b) J32I
c) I34J
d) H32I

Answer: ✅ a) I32J
Explanation:
Letters jump +2; numbers double every step → verified twice.

Answer Key Summary

Q.No Correct Answer Verified
1 QKGYYQG ✅
3 NLNQD ✅
4 CSWKDO ✅
6 10 ✅
7 35 ✅
8 S37C ✅
9 342 ✅
10 835 ✅
13 NSXC ✅
14 2198108 ✅
15 421201018 ✅
16 12027 ✅
17 65 ✅
18 163 ✅
19 I32J ✅

💡 Preparation Tips for Coding-Decoding & Series

  1. Identify repetition patterns:
    Focus on consistent shifts like +2, -3, and vowel-consonant alternation.

  2. Practice reverse order codes:
    Many placement exams use reversed alphabet positions.

  3. Analyze letter-number conversions carefully:
    If you see multi-digit codes, each letter contributes one or two digits.

  4. For number series:
    Focus on differences, ratios, or doubling patterns.

  5. Daily practice = speed.
    Spend at least 20 minutes a day solving logical sequences.