A Civil Servant should be well-versed in basics of Number System. In the Civil Services Aptitude Test Paper 2, in Basic Numeracy, certainly there will be asked some questions based on types of, and operations on numbers.

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.

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