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Alphanumeric Series

Reasoning Ability · Core Logical Tools

Useful for: Railway RRB, IBPS Banking, OSSC RHT — Regular High School Teacher, OSEPA Primary Teacher / JT Category-I, OSEPA Upper Primary — Arts, OSEPA Upper Primary — Science, OSSSC Govt Physical Education Teacher (PET), OSSSC Govt TGT Arts

and 2 more exams

OSSSC Govt TGT Science — CBZ, OSSSC Govt TGT Science — PCM

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Overview

Letter and alphanumeric series move through the alphabet with fixed or changing gaps, sometimes combined with numbers.

Key points

Use positions: B, E, H, K → 2, 5, 8, 11 (+3).
Gaps may increase: A, B, D, G, K (+1, +2, +3, +4).
Alphanumeric terms like A2, C4, E6 combine a letter series and a number series.
Reverse alphabet series move backwards (Z, X, V…).
Missing-letter strings repeat a block: abc_abc_ → find the repeating unit.

Explanation

Split each term into parts and solve each part separately.
For repeating-string questions, count the block length first.
Wrap-around after Z is rare in but possible.
Opposite-letter rules (sum 27) may appear in pairs.

Step by step

Convert to positions.
Find the gap pattern.
Convert back to letters.

Examples

B, E, H, K, ? → +3 → N.
A, B, D, G, K, ? → +1, +2, +3, +4, +5 → P.
A2, C4, E6, G8, ? → letters +2, numbers +2 → I10.

Traps and advanced points

Trap: Counting positions incorrectly.
Trap: Solving letters and numbers as one series.
Trap: Missing the growing gap.

Quick revision

Positions first.
Split letters and numbers.
Find the repeating block.

Practice MCQs

Which option arranges 16, 17, 61, 62 from smallest to largest?
1. 16 < 61 < 17 < 62
2. 16 < 17 < 61 < 62
3. 17 < 16 < 61 < 62
4. 62 < 61 < 17 < 16
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Answer: (b) 16 < 17 < 61 < 62. Compare values and arrange ascending.
Which option arranges 31, 40, 62, 81 from smallest to largest?
1. 40 < 31 < 62 < 81
2. 31 < 40 < 62 < 81
3. 81 < 62 < 40 < 31
4. 31 < 62 < 40 < 81
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Answer: (b) 31 < 40 < 62 < 81. Compare values and arrange ascending.
Which option arranges 47, 62, 64, 82 from smallest to largest?
1. 47 < 62 < 64 < 82
2. 82 < 64 < 62 < 47
3. 62 < 47 < 64 < 82
4. 47 < 64 < 62 < 82
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Answer: (a) 47 < 62 < 64 < 82. Compare values and arrange ascending.
Which option arranges 62, 80, 99, 103 from smallest to largest?
1. 62 < 80 < 99 < 103
2. 103 < 99 < 80 < 62
3. 62 < 99 < 80 < 103
4. 80 < 62 < 99 < 103
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Answer: (a) 62 < 80 < 99 < 103. Compare values and arrange ascending.
Which option arranges 70, 93, 99, 110 from smallest to largest?
1. 110 < 99 < 93 < 70
2. 70 < 99 < 93 < 110
3. 93 < 70 < 99 < 110
4. 70 < 93 < 99 < 110
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Answer: (d) 70 < 93 < 99 < 110. Compare values and arrange ascending.
Which word comes first in dictionary order: Guava, Mango, Kiwi, Date?
1. Kiwi
2. Date
3. Guava
4. Mango
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Answer: (b) Date. Compare letters from left to right.
Which word comes first in dictionary order: Kiwi, Grape, Guava, Cherry?
1. Kiwi
2. Guava
3. Grape
4. Cherry
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Answer: (d) Cherry. Compare letters from left to right.
Which word comes first in dictionary order: Mango, Kiwi, Banana, Grape?
1. Kiwi
2. Mango
3. Grape
4. Banana
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Answer: (d) Banana. Compare letters from left to right.
Find the next letter: C, I, O, U, A, ?
1. I
2. H
3. J
4. G
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Answer: (d) G. Move +6 letters each time.
Find the next letter: F, L, R, X, D, ?
1. M
2. K
3. J
4. L
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Answer: (c) J. Move +6 letters each time.
Find the next letter: F, H, J, L, N, ?
1. P
2. R
3. Q
4. S
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Answer: (a) P. Move +2 letters each time.
Find the next letter: T, W, Z, C, F, ?
1. J
2. K
3. I
4. L
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Answer: (c) I. Move +3 letters each time.
Find the next letter: C, E, G, I, K, ?
1. O
2. P
3. N
4. M
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Answer: (d) M. Move +2 letters each time.
Find the next letter: M, S, Y, E, K, ?
1. Q
2. R
3. T
4. S
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Answer: (a) Q. Move +6 letters each time.
Find the next letter: L, N, P, R, T, ?
1. Y
2. X
3. W
4. V
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Answer: (d) V. Move +2 letters each time.