‘NUMBERS is one of the important topics. In
this chapter, we have put together a number of models of problems. .
For understanding certain mathematical
concepts, it is necessary to know the classification of numbers. The following
is the presentation of types of numbers. .
(1) Natural Numbers
All the counting numbers are called as
natural numbers and are denoted by N. .
Eg: 1, 2, 3, 4, 5, …………….
(a) Even Numbers and Odd Numbers
The numbers which are
exactly divisible by 2 are called as even numbers and which leave a remainder
of one when divided by two are called as odd numbers. .
Eg: 2,4,6,8, …………. are even
numbers. .
Eg: 1,3,5,7, ……….. are odd
numbers. .
(b) Prime
Numbers and Composite Numbers
Any number greater than one
is divisible by unity (one) and itself If a number is not divisible by any
other number except one and itself, it is called a prime number. .
Eg: 2,3,5,7,11, …………. .
Numbers which are divisible
by other numbers along with one and itself are called as composite numbers. .
Eg : 4,6,8,9,10, …………
The number 1 is neither
prime nor composite. .
(2) Whole Numbers
The set of natural numbers plus zero are called
the whole numbers and are denoted by W. .
Eg: 0, 1, 2, 3, …………..
(3) Integers
The whole numbers along with their negatives
are called integers. .
Eg: -4, -3, -2, -1, 0, 1, 2, 3, 4, ……………
Note: (a) Terminating
decimal:
A decimal which contains a
finite number of digits is called a terminating decimal. .
Eg: 
= 0.25; 
= 0.125
(b) Recurring decimal:
A decimal in which a number
or group of numbers are repeated is called as recurring decimal. .
Eg: 1/3 = 0.33333 ………..
Eg: 1/7 = 0.142857142857
………..
We will learn more about
recurring decimals, later in the chapter. .
(4) Rational, Irrational Numbers
Any number which can be expressed as p/q,
where p and q are integers and q 0, is a rational number. In other words, all
rational numbers are integers, terminating decimals (like 0.25, 0.6) or
recurring decimals. Eg. 3/5, 4, -6, 22/7 etc. .
Numbers which are in the form of
non-terminating and non-terminating decimals are termed as irrational words. .
Eg: 
(1.414,...), 
(1.732,...), 
(2,226)…….. are some irrational numbers
