Logical Reasoning 12 Solved Past Papers 2022 to 2025 Archives

Letter Series & Coding-Decoding Past Papers

Solved past paper MCQs for Letter Series & Coding-Decoding from official UHS, NUMS, SZABMU, DUHS, and KMU examinations. Includes verified distractor autopsies and step-by-step cognitive explanations.

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Official printable A4 booklet containing all 12 verified past paper MCQs with unbroken options, 5-column rapid answer key, and Propolis cognitive error autopsies.

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#1 of 12 NUMS 2025
Permalink
What comes next? ZX, WU, TR, QO, ____
A
NL
B
LN
C
NM
D
KH
View Answer & Propolis Autopsy
Correct Key: Option A Diagnostic Explanation
Concept: Alphabetical Decrement Pattern.

Formula: Step back 3 letters per variable.

Solution:

  • \(Q - 3 = N\)


  • \(O - 3 = L\)


Term = NL.

Why other options are incorrect:

• Option B: Incorrect letter ordering.
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#2 of 12 DUHS 2025
Permalink
Identify the next letter in the pattern:

M, N, P, Q, S, ??
A
T
B
U
C
V
D
W
View Answer & Propolis Autopsy
Correct Key: Option A Diagnostic Explanation
Concept: Alphabetical Position Series.

Formula: Sequential pattern of \(+1, +2, +1, +2, +1\).

Solution:

  • M (13) \(\xrightarrow{+1}\) N (14)


  • N (14) \(\xrightarrow{+2}\) P (16)


  • P (16) \(\xrightarrow{+1}\) Q (17)


  • Q (17) \(\xrightarrow{+2}\) S (19)


  • S (19) \(\xrightarrow{+1}\) T (20)


Why other options are incorrect:

• Options B, C, and D: Represent incorrect step sizes.
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#3 of 12 DUHS 2025
Permalink
M, N, P, Q, S, ??
A
T
B
U
C
V
D
W
View Answer & Propolis Autopsy
Correct Key: Option A Diagnostic Explanation
Concept: Letter Progression.

Formula: Alternating \(+1, +2\) step.

Solution: \(S (19) + 1 = T (20)\).

Why other options are incorrect:

• Option B: Adds 2 instead of 1.
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#4 of 12 SZABMU 2025
Permalink
What comes next? ZX, WU, TR, QO, ____
A
NL
B
LN
C
NM
D
KH
View Answer & Propolis Autopsy
Correct Key: Option A Diagnostic Explanation
Concept: Letter Pair Decrement.

Formula: \(-3\) per letter.

Solution: Q(-3)\(\to\)N, O(-3)\(\to\)L \(\implies\) NL.

Why other options are incorrect:

• Option B: Reversed letter pair.
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#5 of 12 DUHS 2024
Permalink
Identify the pattern and choose the correct option that should follow next:

VSA, WRD, XQG, YPJ, _
A
VTC
B
TLK
C
MOZ
D
ZOM
View Answer & Propolis Autopsy
Correct Key: Option D Diagnostic Explanation
Concept: Triple Letter Series.

Formula: Apply distinct positional shifts per letter position.

Solution:

  • 1st letter: V \(\xrightarrow{+1}\) W \(\xrightarrow{+1}\) X \(\xrightarrow{+1}\) Y \(\xrightarrow{+1}\) Z


  • 2nd letter: S \(\xrightarrow{-1}\) R \(\xrightarrow{-1}\) Q \(\xrightarrow{-1}\) P \(\xrightarrow{-1}\) O


  • 3rd letter: A \(\xrightarrow{+3}\) D \(\xrightarrow{+3}\) G \(\xrightarrow{+3}\) J \(\xrightarrow{+3}\) M


Term = ZOM.

Why other options are incorrect:

• Options A and B: Apply backward shifts to the first variable.
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#6 of 12 KMU 2023 Retake
Permalink
Observe the pattern and select the next term in the sequence:

P5QR, P4QS, P3QT, _, P1QV
A
P2QU
B
PQ3U2
C
P2QUY
D
PQ3U
View Answer & Propolis Autopsy
Correct Key: Option A Diagnostic Explanation
Concept: Alphanumeric Sequence Progression.

Formula: Number decrements by 1; last letter advances by 1.

Solution:

  • Number: 5 \(\to\) 4 \(\to\) 3 \(\to\) 2 \(\to\) 1


  • Suffix: R \(\to\) S \(\to\) T \(\to\) U \(\to\) V


Term = P2QU.

Why other options are incorrect:

• Option B: Scrambles variable position.
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#7 of 12 KMU 2023
Permalink
Complete the following series:

KCD, LEF, MGH, _ , OKL.
A
NQM
B
PJI
C
NIJ
D
NJI
View Answer & Propolis Autopsy
Correct Key: Option C Diagnostic Explanation
Concept: Triple-Letter Incremental Pattern.

Formula: \(+1\) shift for first letter, \(+2\) shift for second and third letters.

Solution:

  • 1st letter: K \(\xrightarrow{+1}\) L \(\xrightarrow{+1}\) M \(\xrightarrow{+1}\) N


  • 2nd letter: C \(\xrightarrow{+2}\) E \(\xrightarrow{+2}\) G \(\xrightarrow{+2}\) I


  • 3rd letter: D \(\xrightarrow{+2}\) F \(\xrightarrow{+2}\) H \(\xrightarrow{+2}\) J


Term = NIJ.

Why other options are incorrect:

• Option D: Reverses the last two letters.
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#8 of 12 DUHS 2023
Permalink
If 'blue' is called 'green', 'green' is called 'white', 'white' is called 'red', and 'red' is called 'yellow', what is the color of milk?
A
White
B
Green
C
Yellow
D
Red
View Answer & Propolis Autopsy
Correct Key: Option D Diagnostic Explanation
Concept: Artificial Language Substitution.

Formula: N/A

Solution: Natural color of milk is white. In this code, 'white' is designated as 'red'.

Why other options are incorrect:

• Option A: Uses the uncoded literal color.
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#9 of 12 UHS 2023
Permalink
Observe the pattern and select the next term in the sequence:

SSSSSS, SSRSS, SRQRS, RQPQR, ?
A
RQDQR
B
QRORQ
C
RQPOPQR
D
QPOPQ
View Answer & Propolis Autopsy
Correct Key: Option D Diagnostic Explanation
Concept: Symmetrical Central Letter Shift.

Formula: Inner letters shift backward in alphabet.

Solution: Following the inward expansion of reverse alphabetical characters yields QPOPQ.

Why other options are incorrect:

• Options A and B: Violate the inner character sequence.
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#10 of 12 KMU 2022
Permalink
In a certain language, REMOTE is coded as ROTEME. Which word would be coded as PNIICC?
A
PINCIC
B
PNICIC
C
PICNIC
D
PICCIN
View Answer & Propolis Autopsy
Correct Key: Option C Diagnostic Explanation
Concept: Structural Transposition Coding.

Formula: Swap letters 2\(\leftrightarrow\)4 and 3\(\leftrightarrow\)5.

Solution: Applying the swap rule to PICNIC yields PNIICC.

Why other options are incorrect:

• Option A: Produces incorrect letter ordering.
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#11 of 12 KMU 2022
Permalink
Find the term which does NOT fit into the sequence:

1 CV, 5 FU, 9 IT, 15 LS, 17 OR
A
17 OR
B
5 FU
C
9 IT
D
15 LS
View Answer & Propolis Autopsy
Correct Key: Option D Diagnostic Explanation
Concept: Sequence Anomaly Detection.

Formula: Number pattern = \(+4\); 1st letter = \(+3\); 2nd letter = \(-1\).

Solution:

  • Numbers: 1 \(\xrightarrow{+4}\) 5 \(\xrightarrow{+4}\) 9 \(\xrightarrow{+4}\) 13 (not 15) \(\xrightarrow{+4}\) 17.


  • Letters: C \(\xrightarrow{+3}\) F \(\xrightarrow{+3}\) I \(\xrightarrow{+3}\) L \(\xrightarrow{+3}\) O.


  • Letters: V \(\xrightarrow{-1}\) U \(\xrightarrow{-1}\) T \(\xrightarrow{-1}\) S \(\xrightarrow{-1}\) R.


The term 15 LS breaks the arithmetic number progression (should be 13 LS).

Why other options are incorrect:

• Options A, B, and C: Conform strictly to the arithmetic and alphabetical rules.
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#12 of 12 DUHS 2022
Permalink
What should come next in the series?

7C, 10F, 14J, 19O, ___
A
23Q
B
26N
C
27X
D
25U
View Answer & Propolis Autopsy
Correct Key: Option D Diagnostic Explanation
Concept: Dual Incremental Progression.

Formula: Add consecutive natural integers (\(+3, +4, +5, +6\)).

Solution:

  • Number sequence: 7 \(\xrightarrow{+3}\) 10 \(\xrightarrow{+4}\) 14 \(\xrightarrow{+5}\) 19 \(\xrightarrow{+6}\) 25


  • Letter sequence: C (3) \(\xrightarrow{+3}\) F (6) \(\xrightarrow{+4}\) J (10) \(\xrightarrow{+5}\) O (15) \(\xrightarrow{+6}\) U (21)


Combined term = 25U.

Why other options are incorrect:

• Option A: Uses a constant \(+4\) step on numbers.
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Number Series & Numerical Progressions
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