Business Mathematics and Statistics

The counting numbers 1, 2, 3, 4, .....are called naturals numbers. The set of natural numbers is denoted by 'ℕ'. Thus, ℕ = {1, 2, 3, 4, .....}. 1.1.1 (a) Even Natural Numbers (E): A system of naturals numbers, which are divisible by 2 or are multiples of 2, is called a set of even numbers. It is denoted by 'E'. Thus, E = {2, 4, 6, 8, 10, 12, .....} There are infinite even numbers. 1.1.1 (b) Odd Natural Numbers (O): A system of naturals numbers, which are not divisible by 2 or are not multiples of 2, is called a set of odd numbers. It is denoted by 'O'. Thus, O = {1, 3, 5, 7, 9, 11, .....} There are infinite odd numbers. Taking together the odd and even numbers, we get natural numbers. The number zero is not regarded as natural number. The properties of natural numbers are as follow: (i) Natural numbers are also called counting numbers. (ii) The first and the smallest natural number is 1 (one). (iii) Every natural number (except 1) can be obtained by adding 1 to the previous natural number.