## 1.Number System

Class IX(Chapter 1.Numbers System) 1.Natural Number (N) : All number s used in counting are known as natural numbers such as 1,2,3,….., is called natural number.Denoted by N.N={1,2,3,……,n}. 2.Whole Number(W): All natural numbers including zero , is called Whole numbers.Denoted by W. W={0,1,2,3,…..n}. 3.Integers(I):- All number with +ve and –ve sign including 0, is known … Read more