Number System Class 9 notes with definitions, types, examples, and solved questions for easy revision and better exam preparation.
Introduction to Number System
The number system is the foundation of mathematics. It helps us understand how numbers are represented and used in calculations.
In daily life, numbers are used for counting, measuring, and solving problems. A strong understanding of number systems makes maths easier and builds a base for higher classes.
š For official syllabus and textbook, refer to the NCERT Class 9 Mathematics book
Types of Number Systems
1. Natural Numbers (N)
Counting numbers starting from 1
š Example: 1, 2, 3, 4…
2. Whole Numbers (W)
Includes zero along with natural numbers
š Example: 0, 1, 2, 3…
3. Integers (Z)
Includes positive and negative numbers
š Example: -3, -2, -1, 0, 1, 2
4. Rational Numbers (Q)
Numbers that can be written as p/q
š Example: 1/2, -3/4
5. Irrational Numbers
Cannot be written in p/q form
š Example: ā2, Ļ
6. Real Numbers (R)
Includes both rational and irrational numbers.
Representation on Number Line
All real numbers can be represented on a number line:
Positive numbers ā right side
Solved Examples
Q1. Is ā4 rational or irrational?
š ā4 = 2 ā Rational number
Q2. Write -5/2 in decimal form
š -2.5
Q3. Identify the type of number: 0
š Whole number, Integer, Rational
š Important Points to Remember
Every integer is a rational number
Irrational numbers are non-terminating and non-repeating
Real numbers include all numbers
Negative numbers ā left side
š§ Tips for Students
Learn definitions clearly
Practice number classification
Solve NCERT questions
ā
Conclusion
Number system is the base of mathematics. Once you understand its types and properties, solving questions becomes very easy.
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