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IBPS Clerk Series Completion

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This page covers IBPS Clerk Series Completion with complete concept notes, 17 graded practice MCQs, key points and exam-specific tips. Free to study.

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Concept Notes

Series Completion— Rules & Concept

Core ConceptRead this first — the foundation of the topic
Core Concept

Every series has a hidden logic or pattern. Your job is to crack this pattern and find the next or missing term. The pattern can be based on alphabetical order, numerical gaps, positional values, or combinations

Alphabetical Position Rule

A=1, B=2, C=3...

Gap Pattern

Fixed gaps between consecutive letters 3

Reverse Pattern

Series going backwards in alphabet 4

Alternate Pattern

Two different patterns running together 5

Position-based Pattern

Even/odd positions follow different rules

Formula BlockMemorise — at least one formula appears in every paper
- Alphabetical Position: Letter Position = (Letter ASCII value - 64) for capitals
- Gap Formula: Next term = Current term + Fixed gap

- Alternate Series: Odd positions follow Pattern A, Even positions follow Pattern B

- Reverse Counting: Z=1, Y=2, X=3... A=26
Exam PatternsWhat examiners ask — read before attempting PYQs

SSC loves testing gap-based series (+2, +3, +4 patterns), alternate letter series (AE, BF, CG type), and combination series mixing numbers with letters. Most questions are straightforward if you identify the core pattern quickly.

ShortcutsUse these to save 30–60 seconds per question
#1 - The '5-Second Gap Check'

In any letter series, immediately check if there's a consistent gap between consecutive terms

Count positions

A to D = gap of 3, D to G = gap of 3. If gaps match, you've found your pattern.

Worked ExampleSolve this step-by-step before moving on
1
Step 1

Break into individual letters: A-C, F-H, K-M, P-R

2
Step 2

Find gaps in first letters: A(1) to F(6) = +5, F(6) to K(11) = +5, K(11) to P(16) = +5

3
Step 3

Find gaps in second letters: C(3) to H(8) = +5, H(8) to M(13) = +5, M(13) to R(18) = +5

4
Step 4

Pattern confirmed - both positions have +5 gap

5
Step 5

Next term = P(16)+5 = U(21), R(18)+5 = W(23) Answer: UW Shortcut Trick #2 - The 'Alphabet Skip Method': When you see letters with big gaps, convert to numbers immediately. It's faster to work with 1,6,11,16 than A,F,K,P. Worked Example 2: Complete the series: B2D, D6F, F18H, H54J, ?

1
Step 1

Identify pattern structure - Letter+Number+Letter

2
Step 2

First letters: B,D,F,H (gap of +2 each)

3
Step 3

Last letters: D,F,H,J (gap of +2 each)

4
Step 4

Middle numbers: 2,6,18,54

5
Step 5

Number pattern: 2×3=6, 6×3=18, 18×3=54, 54×3=162

6
Step 6

Next first letter: H+2=J, Next last letter: J+2=L Answer: J162L Shortcut Trick #3 - The 'Reverse Psychology': If normal alphabetical order doesn't work, try reverse order where A=26, B=25, etc. Many SSC questions use this trick. #1 Most Common Trap: Students often miss that a series has TWO separate patterns running simultaneously. They solve for one pattern and ignore the other. Always check if odd and even positions follow different rules. For example, in series ACF, BEH, the first letters follow +2 gap (A,B) while the second and third letters follow different patterns. Another major mistake is confusing alphabetical positions. Remember: A=1, not A=0. This single error can derail your entire solution. Time Management Tip: Spend maximum 90 seconds per series question. If pattern isn't clear in 30 seconds, try the reverse approach or skip and return later.

Key Points to Remember

  • Every letter series follows a hidden pattern - find the logic first, then apply
  • Convert letters to numbers using A=1, B=2... Z=26 for faster calculation
  • Gap Pattern Formula: Check if consecutive terms have fixed gaps (+2, +3, +4)
  • Reverse Pattern Formula: Sometimes A=26, B=25... Z=1 is used
  • Alternate Series Rule: Odd and even positions may follow completely different patterns
  • 5-Second Gap Check: Immediately verify if gaps between consecutive letters are consistent
  • Alphabet Skip Method: Work with numbers (1,6,11,16) instead of letters (A,F,K,P)
  • Two-pattern trap: Most errors occur when students miss that series has dual patterns
  • Time limit: Maximum 90 seconds per question, skip if pattern unclear in 30 seconds
  • Position counting: A=1 not A=0, this basic error ruins entire calculations

Exam-Specific Tips

  • A=1, B=2, C=3... Z=26 is the standard alphabetical position formula used in SSC
  • Most SSC series use gaps of +2, +3, +4, or +5 between consecutive terms
  • Reverse alphabetical counting follows Z=1, Y=2, X=3... A=26 pattern
  • ASCII value formula: Capital letter position = ASCII value - 64
  • Gap Pattern Formula: Next term = Current term + Fixed gap value
  • Alternate Series Formula: Position 1,3,5 follow Pattern A; Position 2,4,6 follow Pattern B
  • Common SSC gaps: +1,+3,+5 (odd gaps) or +2,+4,+6 (even gaps) in same series
  • Mixed series format: Letter+Number+Letter combinations appear in 30% of SSC questions
Practice MCQs

Series Completion — Practice Questions

17graded MCQs · easy to hard · full solution & trap analysis

All MCQs →
Practice 1easy

Complete the series: 1, 4, 9, 16, 25, 36, ?

Practice 2easy

Find the missing term in the series: 2, 5, 10, 17, 26, ?

Practice 3easy

Complete the series: 3, 6, 12, 24, 48, ?

Practice 4easy

What comes next in the series: 5, 8, 11, 14, 17, ?

Practice 5easy

Find the missing number: 2, 3, 5, 7, 11, 13, ?

Practice 6easy

Find the missing term in the series: 3, 6, 12, 24, 48, ?

Practice 7medium

What is the next term in the series: 2, 5, 10, 17, 26, 37, ?

Practice 8medium

Find the missing number: 144, 121, 100, 81, 64, ?, 36

Practice 9medium

What comes next in the series: 1, 1, 2, 3, 5, 8, 13, 21, ?

Practice 10medium

Find the missing term: 5, 11, 23, 47, 95, ?, 383

Practice 11medium

Find the missing term in the series: 3, 6, 12, 24, 48, ?, 192

Practice 12hard

Study the series: 1, 4, 9, 16, 25, 36, 49, 64, ? What is the missing term?

Practice 13hard

Study the series: 5, 7, 11, 19, 35, 67, ? What is the missing term?

Practice 14hard

Study the series: 2, 5, 11, 23, 47, 95, ? What is the missing term?

Practice 15hard

Study the following series carefully and find the missing term: 3, 6, 12, 24, 48, ?, 192 What should replace the question mark?

Practice 16hard

Study the series: 3, 6, 11, 18, 27, 38, 51, ? What is the missing term?

Practice 17hard

Study the series: 2, 3, 5, 8, 12, 17, 23, ? What is the missing term?

60-Second Revision — Series Completion

  • Remember: Convert letters to numbers immediately - A=1, B=2... Z=26
  • Formula: Gap Pattern = Current term + Fixed gap for next term
  • Trap: Always check if odd and even positions have different patterns
  • Shortcut: 5-second gap check - verify consistent gaps between consecutive terms
  • Time: Maximum 90 seconds per question, skip if no pattern in 30 seconds
  • Pattern: Most SSC series use +2, +3, +4 gaps or reverse alphabetical order
  • Error: Never confuse A=1 with A=0, this basic mistake ruins calculations
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