Letter, Letter-Cluster and Alphanumeric Series
Letter, Letter-Cluster and Alphanumeric Series
Letter series are number series in disguise: convert every letter to its position (A = 1 to Z = 26), find the rule, and convert back. Clusters of three or four letters move each position by its own step, and alphanumeric series run a letter rule and a number rule side by side. Fill-in-the-blank series repeat a short block that you must spot.
1. Position Table
| A | B | C | D | E | F | G | H | I | J | K | L | M |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 |
Past Z, continue from A: W + 4 = A (23 + 4 = 27 → 1)
Reverse position = 27 − position: A ↔ Z, M ↔ N
Clusters: track the 1st, 2nd and 3rd letters as three separate series
✗ In DGK, FJO, HMS the whole cluster moves +2 | ✓ Each position has its own step: +2, +3 and +4
✗ W + 4 does not exist | ✓ Wrap round the alphabet: W + 4 = A
हिंदी नोट: अक्षर श्रेणी में हर अक्षर को उसकी स्थिति (A = 1 से Z = 26) में बदलिए। अक्षर-समूह में पहले, दूसरे और तीसरे अक्षर की अलग-अलग श्रेणी बनाइए। Z के बाद फिर A से गिनिए।
Exam Pointer: Verified NTPC patterns: three-letter cluster series (May 2022 CBT-2), alphanumeric clusters (June 2022 CBT-2) and fill-in-the-blanks letter series (April 2021 CBT-1). Single-letter skip series had no separate verified shift and are tagged syllabus-based.
Pariksha Pattern: Every Way NTPC Asks This Topic
Pattern 1: Single letters with growing skips
[Pattern: syllabus-based, PYQ-style]
EXAM LEVEL
Q. Find the next letter: B, E, H, K, ?
Positions 2, 5, 8, 11 rise by 3, so the next is 14 = N.
Answer: N
EXAMATLAS LEVEL
Q. Find the next letter: Z, W, S, N, ?
Positions 26, 23, 19, 14 fall by 3, 4, 5, so the next fall is 6: 14 − 6 = 8 = H.
Answer: H
Pattern 2: Letter clusters
[PYQ: NTPC CBT-2 9-May-2022 Shift-2]
EXAM LEVEL
Q. Find the missing cluster: ABD, CDF, EFH, ?, IJL.
Each position moves +2: A C E G I, B D F H J, D F H J L. The missing cluster is GHJ.
Answer: GHJ
EXAMATLAS LEVEL
Q. Find the missing cluster: DGK, FJO, HMS, ?, LSA.
First letters D F H J L (+2), second letters G J M P S (+3), third letters K O S W A (+4, with W + 4 wrapping to A). The missing cluster is JPW.
Answer: JPW
Pattern 3: Alphanumeric series
[PYQ: NTPC CBT-2 16-Jun-2022 Shift-2]
EXAM LEVEL
Q. Find the next term: A2, C4, E6, G8, ?
Letters skip one (+2) and numbers rise by 2: I10.
Answer: I10
EXAMATLAS LEVEL
Q. Find the next term: B3Y, D6W, G12T, K24P, ?
First letters B D G K move +2, +3, +4, so next +5 = P. Numbers double: 48. Last letters Y W T P move −2, −3, −4, so next −5: 16 − 5 = 11 = K.
Answer: P48K
Pattern 4: Fill in the blanks (repeating blocks)
[PYQ: NTPC CBT-1 6-Apr-2021 Shift-1]
EXAM LEVEL
Q. Fill the blanks in order: a b _ a b c _ b c a _ c
The block "abc" repeats: a b c a b c a b c a b c. The blanks are c, a, b.
Answer: cab
EXAMATLAS LEVEL
Q. Fill the blanks in order: p q _ q q p _ q q _ q q q _
The blocks grow by one q each time: pq, pqq, pqqq, pqqqq, giving p q p q q p q q q p q q q q. The blanks are p, q, p, q.
Answer: pqpq
60-Second Revision
- Convert letters to positions, find the rule, convert back.
- Treat each position in a cluster as its own series.
- Alphanumeric: run the letter rule and the number rule separately.
- Blank series: find the repeating or growing block.