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Revision Notes
Number System — Revision Notes
CAT · Quantitative Aptitude
Free Number System revision notes for CAT Quantitative Aptitude 2026 — key concepts, formulas, and definitions for quick revision.
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Key concepts, formulas, and definitions from Number System for CAT Quantitative Aptitude preparation.
Key Topics to Revise
1
Types of Numbers and Basic Definitions
- Natural Numbers (N): 1, 2, 3, 4... - used for counting, smallest is 1
- Whole Numbers (W): 0, 1, 2, 3... - natural numbers plus zero
- Integers (Z): ...-3, -2, -1, 0, 1, 2, 3... - positive and negative whole numbers
2
Prime Number Properties and Testing
- Smallest prime: 2 (only even prime)
- Smallest odd prime: 3
- Prime checking: Test divisibility only by primes ≤ √n
3
GCD and LCM Concepts
- GCD (HCF): Largest number that divides all given numbers
- LCM: Smallest number that is divisible by all given numbers
- For two numbers: GCD × LCM = Product of numbers
4
Divisibility Rules and Tests
- Divisibility by 2: Last digit is even (0,2,4,6,8)
- Divisibility by 3: Sum of digits divisible by 3
- Divisibility by 4: Last two digits form number divisible by 4
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Key Concepts
Natural numbers (1Prime numbers are natural numbers greaterHCF is the largest numberLCM is the smallest numberRules for quick divisibility checks
Frequently Asked Questions
What topics are covered in Number System for CAT?
Number System is an important chapter in CAT Quantitative Aptitude. It covers key concepts and formulas that are frequently tested in the exam. Key topics include: Types of Numbers and Basic Definitions, Prime Number Properties and Testing, GCD and LCM Concepts, Divisibility Rules and Tests.
How important is Number System for CAT?
Number System is a frequently tested chapter in CAT Quantitative Aptitude. Questions from this chapter appear regularly in previous year papers. There are 67 practice questions available for this chapter.
How to prepare Number System for CAT?
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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