# CBSE 9th Maths

## Number Systems

Natural numbers are - 1, 2, 3, …………….. denoted by N.

• Whole numbers are - 0, 1, 2, 3, ……………… denoted by W.• Integers - ……. -3, -2, -1, 0, 1, 2, 3, ……………… denoted by Z.

• Rational numbers - All the numbers which can be written in the form p/q,q ≠0 are called rational numbers where p and q are integers.

• Irrational numbers - A number s is called irrational, if it cannot be written in the form p/q where p and q are integers and q ≠0

• The decimal expansion of a rational number is either terminating or non terminating recurring. Thus we say that a number whose decimal expansion is either terminating or non terminating recurring is a rational number.

• The decimal expansion of a irrational number is non terminating non recurring.

• All the rational numbers and irrational numbers taken together.

• Make a collection of real number.

• A real no is either rational or irrational.

• If r is rational and s is irrational then r+s, r-s, r.s are always irrational numbers but r/s may be rational or irrational.

• Every irrational number can be represented on a number line using Pythagoras theorem.

• Rationalization means to remove square root from the denominator. 