Quantitative Aptitude Number system notes

5
NUMBER SYSTEMS NOTES


. THEORY
5.1 NUMBER SYSTEM

. A number is a mathematical value used for counting or measuring
or labeling objects.

. Numbers are used to perform arithmetic calculations.


. A number system is an arrangement of expressing the numbers in
written form.

. The number system inter alia facilities addition, subtraction,
multiplication and division.

5.2 TYPE OF NUMBERS
. The various type of numbers including the following:
1. Natural Numbers,
2. Whole Numbers,
3. Integers,
4. Rational Numbers,
5. Irrational Numbers,
6. Real Numbers,

, 5.3 NATURAL NUMBERS
• Natural numbers are a part of the number system, including all
the positive numbers from 1 to infinity.
• The set of numbers is denoted by the symbol ‘N’.
N = {1,2,3,4,5,6,7,..}

• Natural numbers are also known as counting numbers
because they do not include zero or negative numbers.
• There is no greatest natural number whereas the least natural
number is 1.
• Fundamental operations of Natural Numbers are Addition (‘+’),
Subtraction (‘-’), Multiplication (‘*’) and Division (‘/’).
• Addition and multiplication of natural numbers again yield a
natural number but subtraction and and division of two natural
numbers may or may or may not yield a natural number.
• Predecessor and successor.
• If 1 is added to any natural number, we get the next higher
natural number.
• The number before the given number is called as Predecessor.
• The next higher number is called its successor.
Example: The successor of 11 is 11 + 1 = 12 whereas the predecessor
of 11 is 11 – 1 = 10.

5.4 WHOLE NUMBERS
• Whole numbers are a set of numbers including all natural
numbers and 0.
• The set of whole numbers is denoted by the symbol W.