# Free Study Material For RRB Examination: Mathematics (Number System)

## Free Study Material For RRB Examination

Subject : Mathematics (Number System)

In Indian system, numbers are expressed by means of symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, called digits. Here, 0 is called insignificant digit whereas 1, 2, 3, 4, 5, 6, 7, 8, 9 are called significant digits. We can express a number in two ways.

**Notation : **Representing a number in figures is known
as notation as 350.

**Numeration : **Representing a number in words is known
as numeration as ‘Five hundred and forty five’.

## Face Value and Place Value of a Digit

**Face Value: **It is the value of the digit itself eg, in
3452, face value of 4 is ‘four’, face value of 2 is ‘two’.

**Place Value: **It is the face value of the digit
multiplied by the place value at which it is situated eg, in 2586, place value
of 5 is 5 × 102 = 500.

### Number Categories

**Natural Numbers (N): **If N is the set of natural
numbers, then we write N = {1, 2, 3, 4, 5, 6,…}

The smallest natural number is 1.

**Whole Numbers (W): **If W is the set of whole numbers,
then we write W = {0, 1, 2, 3, 4, 5,…}

The smallest whole number is 0.

**Integers (I): **If I is the set of integers, then we
write I = {– 3, –2, –1, 0, 1, 2, 3, …}

**Rational Numbers:** Any number which can be expressed in
the form of p/q, where p and q are both integers and q # 0 are called rational
numbers.