IBPS Clerk · Bite-size lessons

Number Series

About 5 min · Numerical Ability · English

Time worked out from the lesson's 254 words at 150 words a minute, plus a minute for each question.

At Clerk level, the patterns are straightforward compared to PO or RRB PO — you'll rarely see complex nested patterns or obscure sequences.

Key ideas

• Arithmetic Series (Constant Difference): Each term increases or decreases by the same fixed number. Example: 5, 8, 11, 14, ... (difference = +3).
• Geometric Series (Constant Ratio): Each term is multiplied or divided by the same number. Example: 3, 6, 12, 24, ... (ratio = ×2).
• Difference Series with Pattern: The differences themselves form a pattern — increasing by a constant, following squares, or doubling. Example: 2, 3, 5, 8, 12, ... (differences: +1, +2, +3, +4).
• Square-Based Series: Terms are perfect squares, or differences are perfect squares. Example: 1, 4, 9, 16, 25 (squares of 1, 2, 3, 4, 5).
• Cube-Based Series: Terms are perfect cubes, or pattern involves adding/subtracting cubes. Example: 1, 8, 27, 64 (cubes of 1, 2, 3, 4).

Quick reference

• First step always: Calculate differences between consecutive terms.
• No pattern in differences? → Calculate ratios instead.
• Differences increasing by constant amount → Second-level arithmetic series.
• Terms near 1, 4, 9, 16, 25... → Think squares; near 1, 8, 27, 64... → Think cubes.
• Alternating feel → Check if two operations take turns (like +3, ×2, +3, ×2).

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

Read the full noteFlashcards for this topic