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Revision Notes
Series — Revision Notes
BITSAT · Logical Reasoning
Free Series revision notes for BITSAT Logical Reasoning 2026 — key concepts, formulas, and definitions for quick revision.
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Revision Notes — Series
Key concepts, formulas, and definitions from Series for BITSAT Logical Reasoning preparation.
Key Topics to Revise
1
Classification of Series
- All series types fall under three broad categories: Number Series, Alphabet Series, and Alpha-Numeric (Mixed) Series.
- Number Series: terms are purely numerical and related by arithmetic, geometric, or higher-order operations.
- Alphabet Series: terms are letters or groups of letters whose positions in the English alphabet follow a pattern.
2
Number Series – Patterns and Sub-Types
- AP (Arithmetic Progression): constant first difference. Example: 3, 7, 11, 15 … (d = 4).
- GP (Geometric Progression): constant ratio. Example: 2, 6, 18, 54 … (r = 3).
- Second-Order AP: differences themselves form an AP. Example: 1, 2, 4, 7, 11 … (differences: 1, 2, 3, 4 …).
3
Alphabet Series – Patterns and Positional Logic
- English alphabet positions: A=1, B=2, C=3, … Z=26. Positions from the end: A=26, B=25, … Z=1.
- Forward skip series: letters skip a fixed number of positions. Example: A, C, E, G (skip 1 each time).
- Variable skip series: letters skip 1, 2, 3, 4 … positions. Example: G(7), H(8), J(10), M(13), Q(17) — gaps 1,2,3,4.
4
Alpha-Numeric and Mixed Series
- Alpha-Numeric Series: each term contains both a letter (or letters) and a number. Analyse each component independently.
- Example: K1, M3, P5, T7 → letters: K(11), M(13), P(16), T(20) with gaps 2,3,4 → next gap 5 → Y(25); numbers: 1,3,5,7 (odd numbers) → next is 9. Answer: Y9. Wait — re-examining: gaps are 2,3,4,5 → next
- Mixed Series: a long sequence is actually the interleaving of two sub-sequences. Separate odd-indexed and even-indexed terms.
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Key Concepts
A sequence of numbers related byA sequence of letters followingEach term contains both lettersA single sequence that is actuallyA repeating pattern of letters presented
Frequently Asked Questions
What topics are covered in Series for BITSAT?
Series is an important chapter in BITSAT Logical Reasoning. It covers key concepts and formulas that are frequently tested in the exam. Key topics include: Classification of Series, Number Series – Patterns and Sub-Types, Alphabet Series – Patterns and Positional Logic, Alpha-Numeric and Mixed Series.
How important is Series for BITSAT?
Series is a frequently tested chapter in BITSAT Logical Reasoning. Questions from this chapter appear regularly in previous year papers.
How to prepare Series for BITSAT?
Start by understanding the core concepts, then solve practice questions. Focus on formulas and their applications. Use revision notes for quick review before the exam.
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