One to one maths interventions built for KS4 success
Weekly online one to one GCSE maths revision lessons now available
In order to access this I need to be confident with:
Arithmetic Equivalent fractions Simplifying fractions Improper fractions and mixed numbersThis topic is relevant for:
Subtracting Fractions
Here we will learn about subtracting fractions including how to subtract fractions with the same denominator and with unlike denominators (different denominators), and how to subtract mixed numbers.
There are also subtracting fractions worksheets based on Edexcel, AQA and OCR exam questions, along with further guidance on where to go next if you’re still stuck.
What is subtracting fractions?
Subtracting fractions is when we take away one fraction from another or we find the difference between fractions.
To subtract fractions they need to have the same denominator (the same bottom numbers).
Then we can subtract the fractions by subtracting the numerators (the top numbers) and keeping the denominator the same.
The method for subtracting fractions can be modified to add fractions.
E.g.
What is subtracting fractions?
How to subtract fractions
In order to subtract fractions:
- Look at the denominators (bottom numbers) to see if they have a common denominator.
- Subtract the numerators (top numbers).
- Write your answer as a fraction, making sure it is in its simplest form.
Subtracting fractions worksheet
Get your free subtracting fractions worksheet of 20+ questions and answers. Includes reasoning and applied questions.
DOWNLOAD FREE Subtracting fractions worksheet
Get your free subtracting fractions worksheet of 20+ questions and answers. Includes reasoning and applied questions.
DOWNLOAD FREERelated lessons on fractions
Subtracting fractions is part of our series of lessons to support revision on fractions. You may find it helpful to start with the main fractions lesson for a summary of what to expect, or use the step by step guides below for further detail on individual topics. Other lessons in this series include:
Subtracting fractions examples
Example 1: subtracting fractions with a common denominator
Work out
- Look at the denominators (bottom numbers) to see if they have a common denominator.
5 is the denominator for both fractions, so 5 is the common denominator.
2Subtract the numerators (top numbers).
3Write your answer as a fraction, making sure it is in its simplest form.
The final answer is:
2 and 5 do not have a common factor so the fraction cannot be simplified. This fraction is in its simplest form.
Example 2: subtracting fractions with a common denominator
Work out
Look at the denominators (bottom numbers) to see if they have a common denominator.
8 is the denominator for both fractions, so 8 is the common denominator.
Subtract the numerators (top numbers).
Write your answer as a fraction, making sure it is in its simplest form.
The answer is:
This fraction is not in its simplest form as it can be cancelled. Both 2 and 8 are multiples of 2. So 2 is a common factor and can be cancelled:
The final answer is:
Example 3: subtracting fractions with different denominators
Work out
Look at the denominators (bottom numbers) to see if they have a common denominator.
4 is the denominator of the first fraction and 5 is the denominator of the second fraction. These fractions do not have a common denominator.
To be able to subtract the fractions they need to have a common denominator.
4 and 5 have a lowest common multiple of 20, so we change both fractions so that they have a common denominator of 20:
We have converted the fractions so that they have a common denominator and can now be subtracted:
Subtract the numerators (top numbers).
Write your answer as a fraction, making sure it is in its simplest form.
The final answer is:
7 and 20 do not have a common factor so the fraction cannot be simplified. This fraction is in its simplest form.
Alternatively, this question could have been solved by using decimals:
Example 4: subtracting fractions with different denominators
Work out
Look at the denominators (bottom numbers) to see if they have a common denominator.
6 is the denominator of the first fraction and 2 is the denominator of the second fraction. These fractions do not have a common denominator.
To be able to subtract the fractions they need to have a common denominator.
6 and 2 have a lowest common multiple of 6, so we make sure that both fractions have a common denominator of 6 by changing the second fraction:
So we have converted the fractions so that they have a common denominator and can now be subtracted:
Subtract the numerators (top numbers).
Write your answer as a fraction, making sure it is in its simplest form.
The answer is:
This fraction is not in its simplest form as it can be simplified because both 2 and 6 are multiples of 2.
So 2 is a common factor and can be cancelled:
The final answer is:
Alternatively, you could have chosen 12 as a common denominator and cancelled by the common factor of 4 to simplify:
Example 5: subtracting mixed numbers
Work out
Look at the denominators (bottom numbers) to see if they have a common denominator.
As they are mixed numbers it is a good idea to write them as improper fractions (where the numerator is larger than the denominator):
So the question is:
2 is the denominator of the first fraction and 3 is the denominator of the second fraction. These fractions do not have a common denominator.
To be able to subtract the fractions they need to have a common denominator.
2 and 3 have a lowest common multiple of 6, so we change both fractions so that they have a common denominator of 6:
We have converted the fractions so that they have a common denominator and can now be subtracted:
Subtract the numerators (top numbers).
Write your answer as a fraction, making sure it is in its simplest form.
The answer is:
7 and 6 do not have a common factor to cancel, but this fraction is an improper fraction.
It is usually expected that improper fractions are written as mixed numbers:
The final answer is:
Alternatively you could subtract the whole numbers and then subtract the fractions.
Example 6: subtracting mixed numbers
Work out
Look at the denominators (bottom numbers) to see if they have a common denominator.
As they are mixed numbers it is a good idea to write them as improper fractions (where the numerator is larger than the denominator):
So the question is:
2 is the denominator of the first fraction and 5 is the denominator of the second fraction. These fractions do not have a common denominator.
To be able to subtract the fractions they need to have a common denominator.
2 and 5 have a lowest common multiple of 10, so we change both fractions so that they have a common denominator of 10:
We have converted the fractions so that they have a common denominator and can now be subtracted:
Subtract the numerators (top numbers).
Write your answer as a fraction, making sure it is in its simplest form.
The answer is:
19 and 10 do not have a common factor to cancel, but this is an improper fraction.
It is usually expected that improper fractions are written as mixed numbers.
The final answer is:
Alternatively, you could subtract the whole numbers and then subtract the fractions:
Common misconceptions
- Subtracting numerators
When subtracting fractions with common denominators, only the numerators are subtracted.
E.g.
- Mixing up addition and subtraction
Sometimes we can get so involved in making sure the fractions have a common denominator that we forget it is a subtraction.
E.g
This would be wrong as the question has turned into an addition question.
- Remember to use the correct order of operations
When there is addition and subtraction in the same maths sentence, perform the operations in order from left to right as you read them.
E.g.
The correct order is 6 – 1 and then + 2.
Practice Subtracting fractions questions
1. Work out \frac{2}{5}-\frac{1}{5}
2. Work out \frac{3}{8}-\frac{1}{8}
Give your answer as a fraction in its simplest form
3. Work out \frac{4}{5}-\frac{1}{2}
4. Work out \frac{5}{8}-\frac{1}{4}
5. Work out 2\frac{3}{4}-1\frac{1}{3}
Give your answer as a fraction in its simplest form
6. Work out 2\frac{1}{5}-1\frac{2}{3}
Give your answer as a fraction in its simplest form
Subtracting fractions GCSE questions
1. Work out
\frac{4}{5}-\frac{1}{3}(2 marks)
For using a correct common denominator with at least one correct fraction
(1)
=\frac{7}{12}
For the correct final answer
(1)
2. Work out
2\frac{5}{8}-1\frac{1}{3}(2 marks)
For using a correct common denominator with at least one correct fraction
(1)
\frac{63}{24}-\frac{32}{24}=\frac{31}{24}=1\frac{7}{24}
For the correct final answer
(1)
3. Which of these two fractions is closer to 1?
You must show all your working.
(3 marks)
\frac{7}{4}=\frac{49}{28}
and
\frac{4}{7}=\frac{16}{28}
For writing fractions with a common denominator
(1)
\frac{49}{28}-\frac{28}{28}=\frac{21}{28}
and
\frac{28}{28}-\frac{16}{28}=\frac{12}{28}
For finding the difference of the fractions to 1
(1)
\frac{12}{28} is the smallest difference,
So \frac{4}{7} is closer to 1.
For the correct answer with workings
(1)
Learning checklist
You have now learned how to:
- Subtract fractions with the same denominator
- Subtract fractions with different denominators
- Subtract mixed numbers
The next lessons are
Still stuck?
Prepare your KS4 students for maths GCSEs success with Third Space Learning. Weekly online one to one GCSE maths revision lessons delivered by expert maths tutors.
Find out more about our GCSE maths tuition programme.