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Adding fractions with unlike denominators

Adding Fractions with Unlike Denominators

Adding fractions with unlike denominators

Discussion and questions for this video
why does the denominator have to be the same as the other denominator
Good question.
In mathematics, the concept of adding and subtracting fractions require the denominator to be common. The numerator does not need to be common but the denominator must be.
If the denominator wasn't common how would we work out the question?
E.g. 1/3 + 3/7 = ?
To work out this question, we would have to find the LCM (Lowest Common Multiple) of the denominators; in this case, 3 and 7. Then when we find that it is 21, we can adjust the numerators to 7 and 9. With that done, we can add 3 and 7 to make 10 over the denominator, which is 21.

This is why the denominators have to be common. There was no equation or formula built in the concept of adding and subtracting fractions that do not require the denominators to be common.

I hope this clears everything up. :)
Why did he say to turn the nine in to a 36 and why multiply by 4 what.]
nine times four is thirty six but why cant the nine just be nine. I'm confused ):
and why do we have to multiply the numerator by 4 too.~_~
to add fractions, you need to have the denominator the same. these two fractions have denominators of 9 and 12. The lowest common multiple of these two numbers is 36. That requires multiplying by x4 and x3 respectively. We multiply the numerator and denominator by the same number so the number does not change.
4/9 * 4/4 = 16/36. 4/4 is the same as 1, so the number doesn't change
If both denominators are prime numbers, is the only least common multiple between them always going to be the product of the two?
Well, yes because since both are prime numbers, and prime numbers can't divide into each other's multiples, it will have to be the product. For example, 1/5 + 1/7, 7 can't divide into 5's multiples and 5 can't divide into 7's multiples, so the denominator has to be the product. By the way the answer is 7/35 + 5/35 = 12/35
Why do the denominators have to be the same?
You do not have to make them the same but it makes it far easier to do.
why does the denominater have to be greater than the top number?
Excellent question my friend. If you had two fractions like 6/5 and 7/5 you would get 13/5. That is what you would call a improper fraction. In arithmetic you wouldn't leave it like that because it's considered a improper fraction. You would need to change it into a mixed number. When you get to algebra 1 they will allow you to leave it as a improper fraction as an answer to a problem.
I don't get this it is hard can anybody help me?
it is quite simple if you ask me all you have do is this Whenever you add fractions with unlike denominators, you must make the denominators of the same value. In this example, the easiest approach is to multiply 8 x 3 to get 24. Here, you multiply by 3 to get . Then you multiply the second equation by 8 to get . Note that both addends have 24 as a denominator. Add in the same manner as with the unit Adding fractions with like denominators.
can you divide fractions
yes you can beacuse fractions are the answer of 1 divide by a number so yes they can
i cant understand this, how did you get the x3 but the other x4?
Because it is a fraction you can multiply it by anything - it will still be the same fraction of a whole number. (1/2 * 2 is 2/4 - but both are 0.5 in decimal terms)

The objective is to get the denominators the same.
can both fractions be negativs
Right Patrick Crandon!
Is multiplying a fraction as easy as adding and subtracting one?
Multiplying is even easier because you don't have to find any common denominators or anything. You just multiply across: the numerator times the numerator and the denominator times the denominator.
I still don't understand. Please help me i have test next week.
Well when you add a fraction like 4/6 and 9/10 you have to get a common denominator. To do that multiply the denominator 6x10= 60 now the fraction would look like _/60 all we need to do is fine the numerator 6x what = 60 its 10 then we do 10x4 to get the numerator 40/60 do the same thing to the other one now we got 54/60 + 40/60 ok add the numarator 54+40=94 so now we got 94/60 we need t turn it into a mixed number. How much times can 94 go into 60 its 1 time so now we have 1 and 34/60 and thats not your answer yet you have to reduce. So divided by 2 = 17 then 60 divided by 2 is 30 so 17/30.
What if you have a problem where one of the fractions has to be divided into a fraction, and the other number is whole?
If one number is whole, you put it over a denominator of 1. If you have 24/8 - 2, write:
24/8 - 2/1
Hope this helps!
i think you can also just multiply the denominaters by each other........right?
yes, you can just multiply the denominators by each other, but when you use larger numbers, it becomes tedious to multiply all of those giant numbers. It is much simpler to work with smaller numbers, and you are less likely to make a mistake that way. Multiplying the two numbers together is sometimes the only way to get a common denominator.
what if the denominators of two fractions don't have a least common multiple
you work with them in the way as they are - they are already simplified ;)
we are doing this in math and i kinda understand it but its hard also
Agreed, I still think fractions is a pain in the neck, but just work hard and you'll understand it.
do you have fractions with multiplication
Yes they do have fractions with multiplication khan academy.
I do not get the mixed fractions, is there an easier way
What don't you understand about them?
What if both numbers don't have a greatest common factor?
Hi William. Two numbers always have a greatest common factor. Sometimes, it is 1, but often it is larger.
This website has helped me a lot in my school work. Although i am a little confuzzled on how he got his answer, like how did he turn it to a mixed #?
Take a improper fraction like 4/3. Divide the denominator by the numerator. That's 1. How much is left? 1/3, so the mixed number is 1 1/3. This problem doesn't need simplifying, but remember to in other problems if they need it. Hope this helps.
When numerator is greater than the denominator.. it is considered as improper fraction?
Yes it is a improper fraction so you need to turn it into a mixed number.
what if there was an x in the denominator like in the problem 1/x + 4/1
That is a more advanced type of problem, but you can still find a common denominator.
you could multiply 4/1 by x/x and get 4x/x
then add the numerators 1 + 4x, which can't be simplified further.
So the new form is the (1 + 4x)/x also written as

1 + 4x

This isn't really any simpler than the previous expression but they are equal.
what is he trying to say? it is confusing.
it is, why doesn't it have audio
why does the denominator have to be the same?
The denominator has to be the same because then it makes it easier to add, subtract, multiply, or divide the fraction.
What if the Denominator was different from the other Denominator?

That's what were talking about here. "Unlike Denominators" are fractions with- literally- Unlike denominators.
Try the Skill "Adding Fractions" when you're done!
I don't understand. This just confuses me. Can anyone turn this video into something that a 13 yr. old can understand?
I grasped this concept when I was 8. You'll get it, just keep trying.
Because you can only add or subtract the numerator .
on rylireback's comment so just cross multiply
how to find a common multiple?
vote-if u agree that the person who made this website is trying to turn the unlike denominator into a common denominator to make it more easier
Is LCM the only way to add fractions with unlike denominators?
Hi, I was wondering if you were going make 49/36 into a proper fraction like he did... it there any other possible way of doing that? Or is that the only way to covert the improper fraction into a proper fraction? Just wondering! Thanks!
Is there a practice section for adding fraction with unlike Denominator?
There probably is, and you can check the Knowledge Map, but I don't really know for sure.
Thanks for the video but I was sort of confused with how you got the 3.
Make a video that tells me how to simplify a fraction that is NOT an improper fraction!
You need to do the LCD if your Denominator is different at Adding Fractions.
can anyone give an example of what he means
You have to fined a number that goes in to the denominators evenly.... i think Not sure!
Hope that helps
why do you make it so complicated?
I have watched this vidro a hundred times and I still dont get how to add unlike fractions please help!
at2:00 how does it work
If you mean by counting the multiples of 9 to find one that is divisible by 12, you can check every single one (but it's not very efficient), or you can learn the multiples of 9 and 12 up to a certain point. If you mean the multiplying of the denominator as well as the numerator, my teacher always says: "what you do to the bottom you do to the top!" so you make an equivalent fraction.
natasha had sevon eighth gallon of paint.Her brother ivan took one fourth gallon to paint his model boat. Natasha needs at least one half gallon to paint her bookshelf. Did ivan leave her enough paint.
Why do we have covert mixed numbers to improper fractions?
is there adding and subtracting negative fractions with unlike denominators?????i need feedback
Yes, put that in the search box at the top of the page, and it should show you a list of related items.
Why does it have to be unlike denominators?
So how would you do a question like 1/4 - 3/12 ?
Find the least common factor of the denominators (twelve here), find out what to multiply the numerator AND denominator with to achieve a denominator of twelve, i.e. three for the first fraction and one for the second.

Then do the subtraction.

Easy Peasy!
how can i find the word problems for this type of lesson??
If you have a prime number as a denominater and a composite number as a denominater. What do you do if the prime number doesn't go into the composite number?
When subtracting mixed fractions, what if the second fraction is larger than the first? Like 7 3/5 - 5 4/5 = ?
why do u have to multiply the top to
how to i add this mixed fraction the whole number is 6 4-6+5 11/18
why do u need to do a common denominator
Is there another way that you can do this process?
is there any way to do it without changing the denominators?
when you get the answer 1 and 13/39 can you make 13/39 as 1/3
why can't you add them wit the denomenator that the # come with
I am not sure how to add fractions at all how do i
I don't get why we have to multiply
how do u add or subtract butterfly way
why is this so hard i kinda understand but not really who agrees
With finding the LCM, my teacher taught me something called the ladder method. when i ask adults about it, they dont know what that is. is this method useful?
of course!
the ladder method is a modern way of finding LCM
that is why adults dont know about it
why do the fractions have to be simplified?
It is so you can show it in a simplest form and when it comes to percents it will come in handy. From Me
Do you have to simplify both fractions before finding the common denominator?
Add My Bro as Couch: ¸„ø¤º°¨°º¤ø„¸¸„ø¤º°¨
if you are adding 2/4+2/4what does it =
instead of listing the factor could you just multiply them please respond :D
Why would you not simplify this answer, 22/21 to 1 1/21?
The problem was 5/7 + 1/3. In my homework book it said the answer was simply 22/21.
I'm puzzled...someone please explain!
10,020,396 over 300,285,932 plus 125 over 70,000,000. Seems hard. bet you I can fool ya. :)
do i have to change the numoraters.
equations with whole number and fraction
the whole thing was confusing
Why do we have to find a common multiple? Why cant we just the numerators and the denominators together, like we multiply the numerators and the denominators when we are multiplying fractions. I'm confused. Help!

Starting from 3:19 until 3:23, Sal says 9 even though he meant 49.
i just dont get how you simply the fraction please help me
To simplify a fraction, you divide the numerator and denominator by the same numbers until you can no longer divide both the top and bottom by the same number. For example: 4/8 divide the top by 4 and the bottom by 4 and you get 1/2. 1/2 is a simplified fraction.
you cant answer that it dosent make sense fractions only
i don't know how to make the fraction simple
tell me the answer to this 56/93 + 43/94
This section inst for doing your home work.
Srry but i still dont get it and dose not work
hey im new to this and you dont have improper fractions
why did people invent fractions there so HARD!
It's not too hard if you do much exercises.First time I learnt about fractions,I felt it so hard but when I do exercises about it,I felt it easy and I loved it.
i thought that you had to add the different denominators but you have to divide them
so when your multiplying do you have to divide the different denominators and so when your dividing different denominators you have to multiply them
How do you simplify it if it is not an improper fraction?
Is there any other way to do it? I do not understand it very well.
u are soo smart.. just what i need to no except can you do a vidio were you can like turn the inproper fraction into a proper one?? if that makes sence
I was trying to watch Adding fractions with like denominators so I hit watch on the videos page but it brought me to this video - Adding fractions with unlike denominators. WHY???
It comes up in the questions... It helps just to do it all at once.
What do I do to make the answer positive?
what did he say I still don't get it
it is conufseing me i don't now why
Why are both the denominators the same?
If you want to add or subtract a fraction, you have to make both side have the same denominator.
how do i get the answer whne one od the fractions is negatice e.g -3/5 +1/2 ??
This is the way I like to do it:
I just find out what 3/5 - 1/2 is (watch this video: https://www.khanacademy.org/math/arithmetic/fractions/Adding_and_subtracting_fractions/v/subtracting-fractions-with-unlike-denominators) and then make it negative
At 1:29 Sal says three, even though he meant four.
How would you do 4-6/5?
You would have to change the 4 into 3 and 5/5. Still not enough so you would change 3 and 5/5 into 2 and 10/5. Then subtract 2 and 10/5 and -6/5 to get 2 and 1/5. 3 and 5/5 is the same as four. the 5/5 is the same as one
why do you have to multiply by the same number
You have to multiply the same number for the denominator and numerator because whatever you do to the bottom, you do to the top. If you don't do this your fraction would not be equivalent so you would get a different answer because you changed the value of the fraction completely. Hope this helped. :)
I don't get how you did the numbers 9 18 and 27 were wrong yet 36 was right, Can you help me out?
why is it so complicated sometimes?
Adding fractions is only complicated if you forget the rules. Math is so structured and logical that a computer with no ability to reason can be programmed to do it. If you focus on learning the steps, and the overarching principals that get you to the answer rather than "the answer" math will become easier and easier for you.
can you please teach me calculus ?
That's in the calculus section.
where are the problem exercises?
Report a mistake in the video

At 2:33, Sal said "single bonds" but meant "covalent bonds."

Report a mistake in the video

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