State Tamil Nadu Board State Board [Samacheer Kalvi] Class 8th Standard Subject Maths Medium English Download Text Book Document Type PDF

## Samacheer Kalvi Class 8th Chapter Number

Introduction :
Let us recall the different types of numbers which we have already learnt in our earlier classes. When we want to count, it is natural to start with numbers 1, 2, 3, 4, 5, … Isn’t it? These are all called as Counting numbers or Natural numbers and their collection is denoted by . The use of three dots at the end of the list is a notation to show that the list keeps going forever.

Consider the situation that yesterday my purse had money, say `8, but today the purse may be empty. How many rupees are there in the purse now? How to denote this emptiness? Here comes the concept of zero which evolved to symbolize the idea of emptiness. The concept of zero, though quite natural now, was not normal to early humans. Only after hundreds of years people started thinking of it as an actual number. The difficulty was solved when the Indian Mathematicians provided the symbol for zero. The natural numbers system with this additional number zero became Whole numbers.

But, how can a number be negative? Simple! Just think of them as numbers less than zero. Including the negative integers with the whole numbers, we get the list of numbers called the Integers. The integers consist of zero, the natural numbers and the negatives of the natural numbers and it consists a list of numbers that stretch in either direction without end. The entire collection of integers is denoted by Z.

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