Subtracting fractions is easier than you think since it is very similar to adding fractions. Just like adding fractions, you need to keep in mind the following four important rules. Take the quiz to see if you really understand how to subtract fractions.
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As shown in the figure above, the subtraction of 2/8 from 5/8 is simple. Since the denominator is the same, just subtract the numerators.
5/8 - 2/8 = (5 - 2)/8 = 3/8
Example #1:
There is no need to look for a common denominator because they are already the same.
Example #2:
9/4 - 3/4 = (9 - 3)/4 = 6/4
Just like adding fractions, if the denominators are different, you will first find equivalent fractions that give a common denominator for both fractions.
Example #3:
Here the denominators 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.
Example #4:
Here are the three simple steps to follow when subtracting fractions with whole numbers.
Step 1
Convert the whole number into a fraction. You do this by using 1 as a denominator for the whole number.
Step 2
Look for the lowest common denominator. You just need to multiply 1 and the other denominator to get the lowest common denominator.
Step 3
Multiply the numerator and the denominator of the fraction in step 1 by the lowest common denominator.
Step 4
Subtract the fractions.
Example #5:
Subtract: 5 - 1/3
5 - 1/3 = 5/1 - 1/3 = 15/3 - 1/3 = (15 - 1)/3 = 14/3
When subtracting fractions with mixed numbers, just convert the mixed number into an improper fraction before subtracting.
Example #6:
7/3 - 1 2/3 = 7/3 - [(3 × 1 + 2) / 3]
7/3 - 1 2/3 = 7/3 - (5/3)
7/3 - 1 2/3 = (7 - 5)/3
7/3 - 1 2/3 = 2/3