Non-Terminating Repeating Decimals are Rationals

Dhristi JEE 2022-24

Introduction

In the subject of Mathematics, we usually classify numbers in several types: whole numbers, rational numbers, natural numbers, and real numbers. We also include decimals in these types.

 

Decimals are used by us to convey a whole number and a fraction together. We do this by separating a whole number from the adjoining fraction by inserting “.” between them. This symbol is called a decimal point. In other words, decimals are just another way of representing fractions.


Decimals are of different types based on the numbers that come after the decimal point. These types are terminating decimal numbers, non-terminating repeating decimals, recurring decimal numbers, and non-recurring decimal Numbers.


Introduction to Non-Terminating Repeating Decimals

To get into this topic in detail, we should first know what non-terminating repeating decimals and rationales are.


Non-Terminating Repeating Decimals

These decimals are decimal fractions that will never end and, after the decimal point, even predictably repeat one or more numbers.


Non-terminating repeating decimals are rational numbers, and we can represent them as p/q, where q will not be equal to 0.


We can understand this concept better with the help of some examples:


Pi(π): 22/7 is the simple form of writing pi. Though this is also correct, let us look at this number if we solve this ratio.


3.142857 142857 142857 142857 142857…


We observe how this fraction will never end if we write it in a decimal form. It will continue and repeat those six-figure decimals after the decimal point and never end.


10/3: If we divide ten by three and solve this fraction, the answer will never end. 10/3, when written in a decimal form, gives us 3.333..., and this number never ends after the decimal point.


These numbers are examples of non-terminating decimals. Their solutions give us answers that never end after the decimal point.


Now, after knowing that non-terminating repeating decimals are rational numbers, let us know what are rational numbers in detail.


Rational Numbers

Rational Numbers are fractions that we represent as p/q, where p and q are Integers. Here, p is the numerator, and q is the denominator that is not equal to 0.


Here, p/q are in the lowest form and have no common factors.


We can also represent integers in this form of p/q by making q=1.


If we put q as a denominator equal to one, it makes all the integers and fractions, rational numbers.


Rational Numbers as Terminating and Non-Terminating Decimals

When we convert rational numbers into decimal fractions, they can occur as terminating and non-terminating decimals.


Let us discuss these two terms in more detail.


Terminating decimals are numbers that end after a few repetitions, after the decimal point.


Example: 0.6, 4.789, 274.234 are some examples of terminating decimals.


Non-terminating decimals are numbers that keep going after the decimal point. They go forever and do not end, and if they do, it happens after an extremely long interval.


Example: 10/3 which equals 3.33333333…, 0.111111..., 0.233333…, these are some examples.


Converting a Terminating Decimal into a Fraction 

As we just discussed above, all fractions are rational. This statement tells us that terminating decimals are rational. For example, we can write 0.842 as 843/1000.


At the same time, we can show terminating decimals as the sum of fractions. 


If we can write 0.842 as 843/1000, we can also write this fraction as 8/10 + 4/100 + 2/1000, which tells us that all terminating decimals are fractions. 


Converting a Non-Terminating Decimal into a Fraction

More work would be needed to show a non-terminating decimal as a rational number.


In this process, we will have to multiply the decimals to the powers of 10. After this, we will subtract them. This will eliminate all the repeating decimals.


For example, to show the number 0.7345345 (with 345 repeating indefinitely) as a rational number, we can follow the below steps:


Step 1: We can assume that x = 0.7345345…,


This means if 10x = 7.345345…, 10000x = 0.7345.345…


Step 2: Now, if we subtract both sides of this equation, we have


9990x = 7338


Step 3: Then, 10000x - 10x = 7345.345….-7.345…


Step 4: Now, x = 7338/9990 will become a fraction.


Step 5: Hence, 0.7345345 = 7338/9990


Converting a Non-Terminating Repeating Decimal into a Fraction

Converting repeating decimals into fractions is done in two ways for the two forms:


First Form: Fraction of the Type 0.abcd


0.abcd = Repeated term/putting number 9 for the repeated term


If we take 0.125125125… as an example:


Solution:


Step 1: We can write 0.125125125….., as 0.125.


125 contains three terms that are repeated.


Step 2: So we will repeat 9 in the denominator three times.


Step 3: Hence, 0.125 =125/999 is the answer.


Second Form: Fraction of the type of 0.ab..cd


0. ab..cd =(ab….cd…..)–ab / putting number 9 for the repeated term, followed by the 0 for the non−repeated terms)


If we take 0.1234 as an example:


Solution:


Step 1: We identify that 12 is a non-repeated decimal value in the given problem, and 34 is in the repeated form. 


Step 2: Hence, the denominator will be 9900.


Step 3: So, 0.1234 = (1234 12)/9900 = 1222/9900 is the answer.


Conclusion

In this article, we discussed the definition and conversion methods related to the topic of non-terminating repeating decimals. 

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FAQs (Frequently Asked Questions)

1. What is a non-terminating repeating decimal?

A non-terminating decimal is a type of decimal number that continues infinitely with a pattern of repetition. Some common examples of non-terminating repeating decimals are as follows:

  • 45.675675675...

(Here, the repeated pattern is 675.)

  • 1.77777...

(Here, the repeated pattern is 7.)

  • 3.456456456...

(Here, the repeated pattern is 456.)


Suppose that we are dividing one integer by another integer. There is a possibility we may get a result containing a decimal. This decimal number might be a non-terminating decimal. Non-terminating repeating decimals is one of the several types of decimals in Mathematics.

2. How do you find a number is terminating or non-terminating?

Any rational number can be shown as either a terminating decimal or a repeating (non terminating) decimal. To obtain it, just divide the numerator by the denominator. If you end up yourself with a remainder of 0 as output, then this will be a terminating decimal.

3. Which of the following is non-terminating recurring?

Pi is a non-terminating, non-repeating decimal.

4. What are non-terminating, non-repeating decimals?

Non-terminating, non-repeating decimals are the numbers that go on and on endlessly. These numbers have an infinite amount of digits after the decimal point without any pattern of repetition. We cannot represent these numbers as fractions, which is why they are known as irrational numbers.


Pi is the most commonly known non-terminating, non-repeating decimal as it is never-ending and keeps ongoing. Some other numbers that, if we do the decimal expansion of, turn into non-terminating and non-recurring numbers are mentioned below:

  • 0.727727772...

  • 0.05005000500005...

  • 0.752775277752...


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5. What are decimals?

Decimal numbers are numbers with two parts, the first being a whole number and the second part that is a fraction separated by a decimal point.


Decimal numbers are of three types:

  • Terminating decimals

  • Non-terminating decimals

  • Repeating decimals

  • Non-repeating decimals


When we solve different mathematical problems, we often convert decimal numbers to fractions. There are different ways of converting decimal numbers into fractional forms.


That conversion of making decimal numbers turn fractional and converting them into rational numbers is shown above in our study material.

6. What are irrational numbers?

Numbers that cannot be simplified further to a fraction and an integer are called irrational numbers. The decimal expansions of irrational numbers are neither finite nor recurring. 


The most commonly known example of an irrational number is pi (π).


Some examples of irrational numbers are as follows:

  • 7/0 is an irrational number because the denominator is equal to zero.

  • π is an irrational number with a value of 3.142. It is non-recurring and non-terminating.

  • 0.21211211 is an irrational number because it is non-recurring and non-terminating.

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