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How do you do add fractions

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kiss999 | Student, Grade 9 | eNotes Newbie

Posted December 21, 2008 at 11:33 PM via web

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How do you do add fractions

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cburr | Middle School Teacher | (Level 2) Associate Educator

Posted December 22, 2008 at 12:08 AM (Answer #1)

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To add fractions, you have to convert the fractions into the same family.  This is also called ‘finding the common denominator’ – the denominator is the bottom number (or family) and ‘common’ means they are the same.   If you have

½ + ¼   

it is easy to convert, because ½ is the same as 2/4.  So, you get

2/4 + ¼

Now just add the numerators – you have 2 of something and add another 1 of the same thing, you have 3 of them all together.

2/4 + ¼ = ¾

What if you can’t change one of them to be the same as the other?  For example,

1/3 + ¼

You have to find a third number that they both CAN go into – this is called finding the ‘lowest common multiple’.  The new number has to be a multiple of both 3 and 4.  You want the smallest number that works. 

3 x 1 = 3 no

3 x 2 = 6 no

3 x 3 = 9 no

3 x 4 = 12 yes!  4 goes into 12 evenly too

To convert 1/3, multiply TOP AND BOTTOM by how many times 3 goes into 12 -- which is 4.  You get 4/12.  

To convert 1/4, multiply TOP AND BOTTOM by how many times 4 goes into 12 -- which is 3.  You get 3/12. 

4/12 + 3/12 = 7/12 

The key thing to remember is to multiply top and bottom by the same thing. 

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lakeltra | Student | eNotes Newbie

Posted January 22, 2009 at 9:39 AM (Answer #2)

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t0 add you have to wel if the denumenator is the same you add the top number together and leave the bottom the denumenator stays the same.example~1/2 1/2 add 1+1=2/2


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jennifer-taubenheim | Middle School Teacher | (Level 2) Assistant Educator

Posted December 21, 2008 at 11:50 PM (Answer #3)

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In a fraction, the top number is called the numerator and the bottom number is called the denominator.

To add fractions together, the two denominators have to have the same number on the bottom (a common denominator). If they have a common denominator, add the top numbers together and keep the bottom number the same.

EG. 1/3 + 1/3 = 2/3

If the two fractions do not have a common denominator, you have to find one before you can add them. You do this by finding the lowest common multiple (or the smallest number that both can go into. You find equivalent fractions based on the new common denominator and then add.

EG. 1/6 + 1/3

The lowest common multiple would be 6. To change 1/3 into a fraction with a denominator of 6, you would have to multiply the denominator by 2. Then you multiply the numerator by the same number. You multiply the top and bottom by the same number so that the new fraction is an equivalent fraction. This is kind of the opposite of reducing.

1/3 = 2/6

Once you have common denominators, then you can add the two fractions together.

1/6 + 2/6 = 3/6

Then you would reduce the fraction to lowest terms by dividing both the numerator and denominator by the same number.


See one of the websites below for an explanation with images.

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jackandchill | Student , Grade 10 | eNotes Newbie

Posted December 28, 2008 at 3:53 PM (Answer #4)

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Adding fractions you  need to just make sure that all the fractions have the same denominator. Then you can simply add the numerators alone.For that you need to find a LCD.

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saransh2012 | Student | Honors

Posted November 7, 2011 at 9:03 PM (Answer #5)

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In a fraction the top number is called a numerator & the bottom number is called denominator.Example-3/2

In the example 3 is the numerator & 2 is the denominator.If the denominators in the both terms are same then it can easily be added. For example

1/2+3/2 =4/2=2/1=2

If the denominators in the both terms are not same then we can do it by LCM (lowest common mutiple)

Example=LCM of 2,3 and 4

IF there is no number common while doing LCM we can multiply it.



If the denominator is smaller than the numerator it can be converted to mixed fraction.

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Jyotsana | Student , Grade 10 | eNoter

Posted February 21, 2014 at 4:49 AM (Answer #8)

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Example: 2/3+3/4

cross multiply  2*4=8   3*3=9

multiply the denominator  3*4=12

8/12+9/12    you just have to add the numerators


You always have to make sure that both of the denominators are same when you are adding the fractions.

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dracomath | Student , Grade 11 | Honors

Posted December 28, 2008 at 12:37 AM (Answer #6)

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In order to add fractions you must make sure that all fractions have same denominators.  First, find the LCD.  Then, add both numerators.

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revolution | College Teacher | Valedictorian

Posted July 17, 2010 at 11:01 PM (Answer #7)

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First, get a common denominator, meaning find the lowest common multiple  like 2/3 +1/6= 4/6 +1/6

Then, you can add the numerator on top together 4/6+1/6=5/6

If need be, simplify to lowest terms. If not, leave it be.

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