Class 9 Mathematics

NUMBER SYSTEMS

Real Numbers

We started with Natural Numbers and gradually discovered that they were not enough.

Each new situation led us to a larger collection of numbers.

We eventually arrived at two groups:

Rational Numbers

Numbers that can be written as:

p/q

where p and q are integers and q ≠ 0.

1/2    −3/4    5    0

Irrational Numbers

Numbers that cannot be written in the form:

p/q
√2    √3    π

KEY IDEA

Rational and Irrational Numbers together form the Real Numbers.

HOW THE NUMBER SYSTEMS FIT TOGETHER

Real Numbers

Rational Numbers

1/2    3/4    −5/2

Integers

−3    −1    0    1    2

Whole Numbers

0    1    2    3

Irrational Numbers

√2    √3    π

Every Real Number belongs to either the Rational or Irrational group.

NEXT IDEA

We can classify Real Numbers in this way, but there is another way to represent them.

How do Real Numbers look in decimal form?