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Last updated on June 20th, 2025

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Subtraction of Fractions

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Subtraction of fractions involves finding the difference between two fractions. The process depends on whether the fractions have a common denominator or different denominators. It is the process of subtracting the numerators, if the denominators are common, if not then find the LCM and convert them into like fractions and then subtract the fractions. We will now learn more about fractions and how to subtract them.

Subtraction of Fractions for Thai Students
Professor Greenline from BrightChamps

What are fractions?

A fraction represents a part of a whole or a division of a quantity. Fractions consist of two numbers: the numerator, and the denominator. The numerator or also called the top number represents how many parts we have. The denominator is another part of the fraction, the denominator represents the total number of equal parts that make up a whole.

For example, ¾. This means 3 out of 4 equal parts of something. There are many types of fractions. The most common types are mentioned below:

  • Proper Fractions: In proper fractions, the numerator is smaller than the denominator. The fractions are less than one. For example, ½, ¼, ¾.
     
  • Mixed Fractions: Mixed fractions are a combination of a whole number and a proper fraction. A mixed fraction can be converted into an improper fraction. For example, 314, 123, 334.

     
  • Like Fractions: Like fractions are the fractions with the same denominator. For example, 34, 14.
     
  • Unlike Fractions: Unlike fractions are the fractions with different denominators. For example, ½, ¼, ¾.



Some key features of subtraction of fractions are as follows:
Fractions can be subtracted from only when they have the same denominator. The difference between fractions is found by subtracting the numerators.

When fractions have different denominators, we find the LCM or the least common denominator, then convert them to have the same denominator with the help of the LCM.
 

Improper fractions can be subtracted as they are. To find the difference between mixed numbers, change the mixed fraction to an improper fraction and then do the subtraction.
 

To find the difference between mixed fractions where the second fraction is less than the first fraction, subtract the integer parts and fractional parts separately.
 

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How to Subtract Fractions?

How to Subtract Fractions?
To subtract fractions, and get the answer right, we have follow the following steps mentioned below:


Step 1: First, we have to check the denominators, whether they are the like or unlike.


Step 2: If the denominators are different, then we must find the LCM (least common denominator). Then convert the fractions to equivalent fractions using the LCM.


Step 3: Once the denominators are the same, we have to subtract the numerators while keeping the denominator unchanged.


Step 4: Finally, we have to simplify the final answer if the answer can be simplified.


The three types of fractions that can be subtracted are as follows:
 

  • Subtracting Fractions with Unlike Denominators
  • Subtracting Fractions With Whole Numbers
Professor Greenline from BrightChamps

Subtracting Fractions with Unlike Denominators

As we have discussed in the above steps, if we follow the above steps, we can subtract fractions with unlike denominators. For example, subtract 34 - 16.


Step 1: Identify the denominators: 
The denominators are unlike or not the same.


Step 2: Find the LCM:
The LCM of 4 and 6 is 12.

Convert the Fractions:

34 = 3 * 3/4 * 3 = 9/12

1/6 = 1 * 2/6 * 2 = 2/12


Subtract the numerators:

9/12 - 2/12 = 7/12
 

Professor Greenline from BrightChamps

Subtracting Fractions With Whole Numbers:

We can easily subtract a fraction with whole numbers. It is like subtracting fractions. Let us consider an example to understand it better.

Subtract 7 from 19/2

Step 1: As 7 is a whole number, we have to convert 7 into a fraction. To do that, we have to keep 1 as the denominator of 7. So 7 becomes 7/1.


Step 2: Now subtracting fractions as usual:
19/2 – 7/1
= 19/2 – (7 x 2)/(1 x 2)
= 19/2 – 14/2
= (19 – 14)/2
= 5/2.

Professor Greenline from BrightChamps

Real life applications in Subtraction of Fractions

The subtraction of fractions has numerous applications across various fields. Let us explore how the subtraction of fractions is used in different areas:

 

  • Cooking and Baking: We use subtraction of fractions in cooking and baking, where recipes often require subtracting fractional amounts of ingredients. For example, if a recipe calls for ¾ cup of sugar, but you have already added ½ cup, you will need to subtract ½ from ¾ to determine how much more to add.

     
  • Finance:  People use fraction subtraction when dealing with money, discounts, and budgeting. For example, if someone has $534 and spends $212, they need to subtract fractions to find the remaining amount.

     
  • Sports: Subtraction of fractions is also useful in sports and fitness. Athletes track time and distances, often leading to subtraction of fractions to analyze performance improvements. For example, a runner who previously completed a lap in 135 minutes and now finishes in 125 minutes must subtract to find their improvement.
     
Max Pointing Out Common Math Mistakes

Common mistakes and How to Avoid Them in Subtraction of Fractions

Students tend to make mistakes while understanding the concept of subtraction of fraction. Let us see some of the common mistakes and how to avoid them in subtraction of fraction:

Mistake 1

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Subtracting the Denominators Instead of Finding the LCM

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Students must remember that while subtracting fractions with different denominators, they must always find the LCM and convert the fraction into equivalent fractions before performing subtraction.

Mistake 2

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Not Converting Mixed Numbers to Improper Fractions
 

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Students must always convert the mixed fractions to improper fractions before subtracting. This will reduce errors in the final answer.

Mistake 3

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 Forgetting to Borrow When Needed
 

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Students must know if the fractional part of the minuend is smaller than the subtrahend, borrow 1 whole number from the whole number.

Mistake 4

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Not Simplifying the Final Answer: 
 

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Students must always check if the fraction can be simplified after subtraction. If the fraction can be simplified, then it is best to simplify the fraction.
 

Mistake 5

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Ignoring Negative Fractions
 

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Students must remember to subtract properly and check if the result is negative. If the result is negative, they must denote it as such.

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Solved examples on Subtraction of Fractions

Ray, the Character from BrightChamps Explaining Math Concepts
Max, the Girl Character from BrightChamps

Problem 1

Subtract 7/10 - 3/10?

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2/5

Explanation

Same Denominator:

Both fractions share the denominator 10.

Subtract Numerators:

7 − 3 = 4

Keep the denominator:

4/10

Simplify the fraction:

4/10 = 2/5
 

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Problem 2

Subtract 3/4 - 1/6

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7/12

Explanation

 Find LCM:

The LCM of 4 and 6 is 12.

Convert the Fractions:

3/4 = 3 * 3/4 * 3 = 9/12

1/6 = 1 * 2/6 * 2 = 2/12

Subtract the numerators:

9/12 - 2/12 = 7/12
 

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Problem 3

Subtract 5/8 - 1/3

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7/24

Explanation

Find LCM:

LCM of 8 and 3 is 24. 

Convert fractions:

5/8 = 5 * 3/8 * 3 = 15/24

1/3 = 1 * 8/3 * 8 = 8/24

Subtract the numerators: 

15/24 - 8/24 = 7/24
 

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Problem 4

Subtract 2/5 - 3/5

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1/5

Explanation

Same Denominator:

Both fractions have 5 as the denominator.

Subtract Numerators:

2 − 3 = −1

Combine: 

-1/5
 

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Problem 5

Subtract 3 1/4 − 1 2/3

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1 7/12

Explanation

Convert to improper fractions:


3 1/4 = 3 * 4 + 1/4 = 13/4


123 = 1 * 3 + 2/3 = 5/3

Find LCM:

LCMs 4 and 3 are 12.

Convert fractions:

13/4 = 13 * 3/4 * 3 = 39/12

5/3 = 5 * 4/3 * 4 = 2012

Subtract numerators:

39/12 - 20/12 = 19/12

Convert back into mixed fraction:

1 7/12
 

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FAQs on Subtraction of Fractions

1.What is the subtraction of fractions?

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2.What is an LCM?

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3.Why is LCM important?

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4.Do I need to simplify the fraction after subtracting?

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5.What is the importance of simplifying fractions after subtraction?

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6.How can children in Thailand use numbers in everyday life to understand Subtraction of Fractions?

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7.What are some fun ways kids in Thailand can practice Subtraction of Fractions with numbers?

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8.What role do numbers and Subtraction of Fractions play in helping children in Thailand develop problem-solving skills?

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9.How can families in Thailand create number-rich environments to improve Subtraction of Fractions skills?

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Hiralee Lalitkumar Makwana

About the Author

Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.

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Fun Fact

: She loves to read number jokes and games.

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