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Series (Logic) Solved Questions & Notes (2026) - Apex Rankers

General Competitive Exams > Logic > Series

21 Total Solved Questions
~32 mins Estimated Reading Time
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Q. 1 Intelligence Tests
Difficulty: Hard (1 Mark)
Series: Aoz, Boy, Cox, Dow, ——
A
Goy
B
Dox
C
Eou
D
Eov
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
First letters: A-B-C-D-E. Second: o-o-o-o-o. Third: z-y-x-w-v. Result: Eov.
Q. 2 Intelligence Tests
Difficulty: Hard (1 Mark)
Series: 27, 5, 25, 8, 23, 11, 21, ——
A
15, 21
B
14, 19
✓ Correct
C
16, 23
D
12, 19
💡 Step-by-Step Explanation & Concept Rationale
Two alternating series: 27-25-23-21 (-2) and 5-8-11 (+3). Next terms: 19 and 14.
Q. 3 Intelligence Tests
Difficulty: Hard (1 Mark)
ABCD ;DCBA;WXYZ;?
A
XZYW
B
YZYW
C
ZYXW
✓ Correct
D
WXYZ
💡 Step-by-Step Explanation & Concept Rationale
The second set is the reverse alphabetical order of the first; W-X-Y-Z reversed is Z-Y-X-W.
Q. 4 Intelligence Tests
Difficulty: Hard (1 Mark)
AZ CX EV------?
A
UB
B
GT
✓ Correct
C
DW
D
EV
💡 Step-by-Step Explanation & Concept Rationale
This is a sequence of pairs from opposite ends of the alphabet (A-Z, C-X, E-V); the next odd letter is G (7th), paired with T (20th).
Q. 5 Intelligence Tests
Difficulty: Hard (1 Mark)
ACE BDF CEG---?
A
DEM
B
CED
C
CED
D
DFH
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Each group shifts forward: A-C-E (+1 shift) -> B-D-F -> C-E-G -> D-F-H.
📜 Instructions / Reading Passage
2 Questions in this set
Test of Alertness: Point out the correct choice based on the logic provided in each problem.
Q. 6 Intelligence Tests
Difficulty: Hard (1 Mark)
Complete the series: AACBBBDCCCE -----, -----,
A
EE
B
ED
C
DE
D
DD
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
The series intersperses a single letter (C, D, E) between growing groups of duplicated letters (AA, BBB, CCCC, DDDDD).
Q. 7 Intelligence Tests
Difficulty: Hard (1 Mark)
In the series 67, 57, 52, 42, 37, 27, 22, X, Y. (c) Both statements at A and D are correct
Correct Answer / Solution Key:
(c)
💡 Step-by-Step Explanation & Concept Rationale
Pattern: -10, -5, -10... result is X=12, Y=7. Key validates choice (c) covering this result.
📜 Instructions / Reading Passage
1 Question in this set
Passage Evaluation: Read the statements below, carefully paying attention to their relation to one another. Then next to each statement mark (a), (b), (c) or (d) as indicated: (a) Central idea; (b) Main supporting idea; (c) Illustrative fact or detailed statement; (d) Irrelevant idea.
Q. 8 Intelligence Tests
Difficulty: Hard (1 Mark)
In the series 45, 35, 30, 20, 15, P, Q. (X) Q is -5 (Y) P is +5
A
Both are correct
B
Y correct but X incorrect
C
X is correct
D
Statement Y is correct
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Pattern is -10, -5... P = 15−10=5; Q = 5−5=0. Thus Y is correct and X is wrong.
📜 Instructions / Reading Passage
2 Questions in this set
ALPHABETICAL SERIES: Identify the missing letter or group of letters in the provided sequence based on increasing/decreasing gaps or alternating patterns.
Q. 9 Intelligence Tests
Difficulty: Hard (1 Mark)
W T P M I ?
A
K
B
P
C
F
✓ Correct
D
I
💡 Step-by-Step Explanation & Concept Rationale
Alphabet sequence skipping letters: W(-3)T(-4)P(-3)M(-4)I. Next skip is -3: F.
Q. 10 Intelligence Tests
Difficulty: Hard (1 Mark)
A D G D H I H M ?
A
C
✓ Correct
B
K
C
L
✓ Correct
D
R
💡 Step-by-Step Explanation & Concept Rationale
This sequence is broken down into overlapping groups of three letters (triplets). Each new triplet begins with the last letter of the previous one:
Group 1: A, D, G
Group 2: D, H, I
Group 3: H, M, ?

If we look at how the alphabet numerical positions (A=1, B=2, etc.) change across each corresponding spot in the triplets, a clear mathematical pattern emerges:
1st letter of each group: A (1) → D (4) → H (8) (Increases by +3, then +4)
2nd letter of each group: D (4) → H (8) → M (13) (Increases by +4, then +5)
3rd letter of each group: G (7) → I (9) → ? (Following the progression, it must increase by +2, then +3)

Adding 3 to the position of I (9) gives us 12, which corresponds to the letter L.
📜 Instructions / Reading Passage
11 Questions in this set
ALPHABETICAL SERIES: Identify the missing letter or group of letters in the provided sequence based on increasing/decreasing gaps or interleaved patterns (squares, evens, multiples).
Q. 11 Intelligence Tests
Difficulty: Hard (1 Mark)
M N O L R I V ?
A
S
B
T
C
E
✓ Correct
D
D
💡 Step-by-Step Explanation & Concept Rationale
Alternating series: (M, O, R, V) shifts +2, +3, +4; (N, L, I, ?) shifts -2, -3, -4. I(9)−4=5(E).
Q. 12 Intelligence Tests
Difficulty: Hard (1 Mark)
C B A E D Z G F ?
A
X
B
H
C
Q
D
Y
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Squares interleaved with reverse pairs: 1→26(Z),26→25(Y).

CB with A
ED with Z
GF with Y
Q. 13 Intelligence Tests
Difficulty: Hard (1 Mark)
A B D G ? P
A
C
✓ Correct
B
E
C
K
✓ Correct
D
J
💡 Step-by-Step Explanation & Concept Rationale
Increasing gap sequence: A(+1)B(+2)D(+3)G(+4)K(+5)P.
Q. 14 Intelligence Tests
Difficulty: Hard (1 Mark)
J Z I Y H ?
A
A
B
X
✓ Correct
C
U
D
Z
💡 Step-by-Step Explanation & Concept Rationale
Alternating descending series: (J, I, H) moves -1; (Z, Y, ?) moves -1 to X.
Q. 15 Intelligence Tests
Difficulty: Hard (1 Mark)
W T P M I ?
A
G
B
H
C
F
✓ Correct
D
L
💡 Step-by-Step Explanation & Concept Rationale
Descending gaps pattern: -3, -4, -3, -4; next is -3 (9−3=6) which is F.
Q. 16 Intelligence Tests
Difficulty: Hard (1 Mark)
R T P R N P ?
A
B
B
D
✓ Correct
C
Q
D
L
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Alternating series: (R, P, N, ?) moves -2 to L; (T, R, P) moves -2.
Q. 17 Intelligence Tests
Difficulty: Hard (1 Mark)
D F G J K M N Q R T ?
A
EL
B
UX
✓ Correct
C
NO
D
UV
💡 Step-by-Step Explanation & Concept Rationale
Gap pattern of +2, +1, +3 repeats; starting at T(20), +1 gives U, +3 gives X.
Q. 18 Intelligence Tests
Difficulty: Hard (1 Mark)
H I J I K L M L N O ?
A
PO
✓ Correct
B
HL
C
IP
D
ST
💡 Step-by-Step Explanation & Concept Rationale
Triplets follow (+1, +1, -1): HIJI, KLML, so NOPO completes the logic.
Q. 19 Intelligence Tests
Difficulty: Hard (1 Mark)
A E I M Q ?
A
V
B
W
C
N
D
U
✓ Correct
💡 Step-by-Step Explanation & Concept Rationale
Constant alphabet shift of +4: A(1), E(5), I(9), M(13), Q(17), U(21).
Q. 20 Intelligence Tests
Difficulty: Hard (1 Mark)
B F K Q ?
A
P
B
S
C
X
✓ Correct
D
D
💡 Step-by-Step Explanation & Concept Rationale
Increasing gaps between letters: +4, +5, +6; next shift is +7 (17+7=24) resulting in X.
Q. 21 Intelligence Tests
Difficulty: Hard (1 Mark)
A F I D H Y L E J ?
A
Q
B
S
C
O
✓ Correct
D
P
💡 Step-by-Step Explanation & Concept Rationale
Three interleaved series: Squares (A,D,I,Y), Evens (F,H,L), Multiples of 5 (E,J,O).
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