Number System
Gujarat Board · Class 9 · Mathematics
Complete topic list for Number System in Gujarat Board Class 9 Mathematics. Key concepts, sub-topics, and what to focus on for board exams.
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Get startedTopics in Number System
Types of Numbers – The Complete Picture
- Natural Numbers (N): 1, 2, 3, 4, ... — counting numbers, starting from 1
- Whole Numbers (W): 0, 1, 2, 3, ... — natural numbers plus zero
- Integers (Z): ..., -3, -2, -1, 0, 1, 2, 3, ... — includes negative numbers, zero, and positive numbers
Irrational Numbers and Their Properties
- Irrational numbers were first discovered by the Pythagoreans around 400 BC
- √2 was the first irrational number proved to be irrational
- Examples of irrational numbers: √2, √3, √5, √7, π, 0.10110111011110...
Decimal Expansions of Real Numbers
- Every rational number has a decimal expansion that is either TERMINATING or NON-TERMINATING RECURRING
- Every irrational number has a decimal expansion that is NON-TERMINATING NON-RECURRING
- Terminating decimal: remainder becomes zero after some steps. Example: 7/8 = 0.875
Operations on Real Numbers
- Rational + Rational = Always Rational
- Irrational + Irrational = Can be rational OR irrational. Example: √2 + (-√2) = 0 (rational); √2 + √3 (irrational)
- Rational + Irrational = Always Irrational. Example: 2 + √3 is always irrational
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