Number system of class 9 | Number System

NUMBER SYSTEM

Even numbers:- The numbers which are the multiples of 2 or which come in the table of 2 are called even numbers eg. 2,4,6,etc

Odd numbers:- The numbers which are not the multiples of 2 are called odd  numbers eg. 1,3,5,7, etc.

Prime numbers:- The numbers which have only two factors are called prime numbers eg. 2, 3 ,5 ,7, 11, 13 , 17 etc.

All prime numbers from 1-100

There are total 25 prime numbers from 1 to 100. These are

2 , 3 ,5 ,7 , 11 , 13 ,17, 19 , 23, 29 , 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.

Composite numbers :- The numbers which have more than two factors are called composite numbers eg. 4, 6. 8 ,9 etc.

Note:- 

1).  1 is neither prime nor composite.

2).  2 is only even prime number. 

Co-prime Numbers :- The two numbers which do not have any common factor other than 1 are called coprime numbers. 

                         or 

The two numbers whose HCF is 1 are called coprime numbers.

Eg. (3,4) ; (5,9) etc.

Twin prime numbers:- Two prime numbers  which have a difference of 2 are called twin prime numbers.

For example (3,5) ; (5,7) ; (11,13) ; (17,19) ; (29,31) ; (41,43) ; (71,73) etc.

Natural numbers :- Counting numbers are called natural numbers eg. 1,2,3,45 etc.

Whole numbers :- All counting numbers alongwith 0 are called whole numbers eg 0,1,2,3,4 etc.

Integers :- All natural numbers, their negatives alongwith 0 are called Integers eg.     ..........-3, -2, -1 , 0 , 1 ,2 ,3........

Rational numbers :- The numbers which can be written in the form of p/q where p and q are integers and q not equal to zero are called rational numbers. Eg. 1/2 , -6 , 0 , 4/7 etc.

Irrational numbers :- The numbers which can not be written in the form of p/q where p and q are integers and q not equal to zero sre called irrational numbers. Eg. √2 , √5 etc.

Real numbers :- The collection of all rational numbers and irrational numbers are called real numbers eg. 3/5, 0 , 6 . -3, √7 etc.