Class 9 Mathematics

NUMBER SYSTEMS

Decimal Representation of Real Numbers

We have seen that Real Numbers include both Rational and Irrational Numbers.

But how do these numbers appear when we write them in decimal form?

Consider:

1/2 = 0.5

The decimal ends after a finite number of digits.

Such a decimal is called a terminating decimal.

Now consider:

1/3 = 0.333...

The decimal does not end, but the digit 3 keeps repeating.

This is called a non-terminating recurring decimal.

Now look at an Irrational Number:

√2 = 1.414213562...

Its decimal representation does not end and does not repeat in a fixed pattern.

This is called a non-terminating non-recurring decimal.

KEY IDEA

Rational and Irrational Numbers have different types of decimal representations.

THE PATTERN

Rational Numbers have decimal representations that either terminate or eventually repeat.

Rational → Terminating or Recurring

Irrational Numbers have decimal representations that continue forever without repeating.

Irrational → Non-terminating & Non-recurring

NEXT IDEA

We now know that Rational Numbers can have terminating or recurring decimals.

But why does this happen?