Subtracting fractions


Subtracting fractions is easier than you think and it is very similar to adding fractions

Just like adding fractions, there are two important things you need to know:

First, you cannot add the denominators; you can only add the numerators

Second, you can only add the numerator when the denominator is the same for both fractions. Your denominator will stay the same.

Having said that, just like adding fractions, if the denominators are different, you will first find equivalent fractions that give a common denominator for both fractions

Example #1:

5 / 2
 − 
1 / 2
= ?


There is no need to look for a common denominator because they are already the same

So,  
5 / 2
 − 
1 / 2
 = 
5 − 1 / 2
 = 
4 / 2
= 2


Example #2:

7 / 3
 − 
3 / 6
= ?


Here the denominator are not the same, so multiply 3 by 2 to get the same denominator

Remember that we have to multiply 7 by 2 also in order not to change the problem

So,  
7 / 3
 − 
3 / 6
 = 
7 × 2 / 3 × 2
 − 
3 / 6
 = 
14 / 6
 − 
3 / 6
 = 
11 / 6


Example #3:

3 / 5
 − 
2 / 4
= ?


So,  
3 / 5
 − 
2 / 4
 = 
3 × 4 / 5 × 4
 − 
2 × 5 / 4 × 5
 = 
12 / 20
 − 
10 / 20
 = 
2 / 20


5 / 2
 − 
1 / 2
= ?


There is no need to look for a common denominator because they are already the same

So,  
5 / 2
 − 
1 / 2
 = 
5 − 1 / 2
 = 
4 / 2
= 2


Example #2:

7 / 3
 − 
3 / 6
= ?


Here the denominator are not the same, so multiply 3 by 2 to get the same denominator

Remember that we have to multiply 7 by 2 also in order not to change the problem

So,  
7 / 3
 − 
3 / 6
 = 
7 × 2 / 3 × 2
 − 
3 / 6
 = 
14 / 6
 − 
3 / 6
 = 
11 / 6


Example #3:

3 / 5
 − 
2 / 4
= ?


So,  
3 / 5
 − 
2 / 4
 = 
3 × 4 / 5 × 4
 − 
2 × 5 / 4 × 5
 = 
12 / 20
 − 
10 / 20
 = 
2 / 20


Subtracting fractions quiz. See how well you can subtract fractions.




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