NUMBERS
NUMBERS

A number is a mathematical object used to count and measure. A notational symbol that represents a number is called a numeral but in common use, the word number can mean the abstract object, the symbol, or the word for the number.

Number is first discovered in India and ten symbols are used, namely o, 1, 2, 3, 4, 5, 6, 7, 8 and 9 to represent any number. These symbols are called digits.

A group of digits, denoting a number, is called a numeral. Every digit in a numeral has two values:
a.    Its face value is equal to it and never changes.
b.    Its place value depend on its position in numeral.
 
1.    Natural Number       : N = {1, 2, 3, 4, 5, 6, 7, 8, 9, …… 8} (0 excluding)
2.    Whole Numbers       : W= {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, …… 8} (0 including) . All natural numbers are whole numbers. 0 is only a       whole number and not a natural number. Aaryabhatt, who was an astronomer and lived in India around 500 AD, invented the    symbol 0 for nothing.
3.    Even Number          : E={2, 4, 6, 8, 10 ………………..}
4.    Odd Numbers          : O={1, 3, 5, 7, 9, 11, ……}
5.    Positive integers      : I+ = {+1, +2, +3, …….}
6.    Negative Integers    : I- = {-1, -2, -3, -4,…………..}
7.    Integers                 : I= {…-4,-3,-2,-1,0,1,2,3,4…..}     
8.    Zero                       :
       a.    Zero is an integer and it is neither positive nor negative.
       b.    Any number multiplied by 0 is equal to 0.
       c.    Face value and place value of 0 is always 0
       d.   Zero is nither even nor odd 
 
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