Adding and Subtracting Fractions

By: Marwa and Jaymie

Subtracting Fractions

First Method- regular fractions

Question: 3/5 - 2/3



First, all you do is list the multiples of each denominator... 5,10,15

3,6,9,12,15

As you can see the common denominator is 15,

Now that we know the common denominator we have to multiply

5 multiplied by 3 gives us 15 and 3 multiplied by 5 gives us 15

remember anything you do to the denominator you HAVE to do to the numerator


3 x 3 2 x 5

____ -- ____

5 x 3 3 x 5


so our fractions are now... 9/15 - 10/15

now that we have the denominators the same we can simply subtract the numerators


9-10=1


Answer= 1/15---remember the denominator always stays the same.

Learn Fractions - How to Subtract Fractions
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Second Method- improper fractions

Question: 15/2 - 10/5


First, we find the common denominator

5,10

2,4,6,8,10

As you can see 10 is the common denominator,now its time to multiply

5 multiplied by 2 is 10 and 2 multiplied by 5 is 10

remember anything you do to the denominator you must do to the numerator


15 x 5 10 x 2

_______ --- ________

2 x 5 5 x 2


our fractions are now.... 75/10 - 20/10


After that we simply subtract the numerators

75 - 20 = 55


Answer: 55/10

In this example the answer can be reduced and since this is a improper fraction we have to turn it into a mixed number, so we have to see how many times the denominator goes into the numerator, 10 goes into 55 , 5 times so 5 will be our whole number and the remainder is 5 and the denominator stays the same so it will be 10 so it will look like this .........



Final Answer: 5 5/10


Whole #=5

remainder =5

denominator=10

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Third Method- mixed numbers

Question: 1 11/6 - 2 2/3


First, we have to turn each mixed number into an improper fraction

and to do that we have first multiply the whole number and the denominator and then add the numerator so 1 x 6 + 11 = 17/6 and 2 x 3 + 2 = 8/3 ---- remember the denominators always stay the same


Now that we have the improper fractions we must find the common denominators

6,12

3,6

As you can see 6 is the common denominator, 6 x 1 is 6 and 3 x 2 is 6 so...


17 x 1 8 x 2

______ ---- ______

6 x 1 3 x 2


our fractions are: 17/6 - 16/6


now that we have that we can simply subtract the numerators

17-16=1

Answer: 1/6

How to Convert Fractions into Mixed Numbers
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Subtracting mixed numbers

Adding Fractions