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## Adding fractions with unlike denominators

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why does the denominator have to be the same as the other denominator
It makes the process a lot easier, but you don't have to. Just find the common denominator and multiply, divide, add, or subtract. Using graphs or charts such as the pie chart also helps understand the basic concept of it.
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what if the denominators of two fractions don't have a greatest common divisor, like in 3/10 + 3/7? What do you do? Please help!
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you look for the least common multiple(the least both of them will multiply into)
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If both denominators are prime numbers, is the only least common multiple between them always going to be the product of the two?
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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
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can both fractions be negativs
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check the number line. can you add two negative numbers? the answer is yes.
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I don't get this it is hard can anybody help me?
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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.
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how do you subtract a broblem
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You first use the same method as shown in this video to find common denominators.

Once the denominators are alike, the fractions can be added or subtracted.

Here is a video on "Adding and Subtracting fractions" with like denominators.
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Why do the denominators have to be the same?
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You do not have to make them the same but it makes it far easier to do.
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why does the denominater have to be greater than the top number?
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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.
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i cant understand this, how did you get the x3 but the other x4?
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If you're adding a fraction, you must have denominators that are alike. For example, if you are adding 1/4 + 1/3, you have to make both the denominators the same. So the lowest common denominator for 4 and 3 is 12, so you would multiply 1/4 by 3 and get 3/12. Then you would multiply 1/3 by 4 because you need to get the denominator to 12, and 3 times 4 is 12. So you would get 4/12. Now you would add 3/12 and 4/12 together and get 7/12.
I hope this helped and good luck!
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What happens when the denominators don't have a common multiple thing?
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why does the denominator have to be the same?
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The denominator has to be the same because then it makes it easier to add, subtract, multiply, or divide the fraction.
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I do not get the mixed fractions, is there an easier way
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What don't you understand about them?
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what if there was an x in the denominator like in the problem 1/x + 4/1
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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
--------
x

This isn't really any simpler than the previous expression but they are equal.
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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 #?
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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.
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we are doing this in math and i kinda understand it but its hard also
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Agreed, I still think fractions is a pain in the neck, but just work hard and you'll understand it.
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i think you can also just multiply the denominaters by each other........right?
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Not exactly... It does involve multiplication, yes, but, what you need to do is find the common denominator( a denominator that both of the fractions can multiply into and get)
like 4/5 and 6/30. the common denominator would be 30, cause 5 can multiply into 30. if you multiply 5 by 6 to get 30, you would also need to multiply the numerator by that same number that you multiplied the denominator by.
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What if both numbers don't have a greatest common factor?
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Hi William. Two numbers always have a greatest common factor. Sometimes, it is 1, but often it is larger.
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Is there a vid for simplest form???????
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what if the denominators of two fractions don't have a least common multiple
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you work with them in the way as they are - they are already simplified ;)
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What does it mean to simplify the problem?
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If you're simplifying something it could mean:
-you need to answer the problem or
- you need to simplify a fraction, like 2/4 -->1/2
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what is he trying to say? it is confusing.
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do you have fractions with multiplication
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Yes they do have fractions with multiplication khan academy.
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If there is no common denominator(except for multiplying the two numbers, of course.)
does it have to be the product of the two numbers?
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How do you add fractions with unlike fractions can anyone give me some steps
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I don't really understand how to simplify. It is confusing to me somehow and everytime I get a question that asks me to simplify I can't do it, I don't understand it. Can somebody please help me figure it out?
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I was going through the adding mixed fractions with unlike denominators and simplifying them to their lowest term and I am so lost right now. I had to watch the videos like five times. I am just trying to figure it out.
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how about if we have like 36, and we have to find a GCF, and we have to do 2. what can save me from doin all that work?
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i dont know but good question.
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i still dont get nothing by the way dont put my question at the bottom
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i dont get it
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Why does the denominator have to change? Why can't it be just the same denominators as the Like Denominators? I don't get it.
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the denominator has to change because you are breaking something up into more parts
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Why can't we just add it normally like when you multiply fractions?
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i don't know wish you could though
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This site is asome.
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How would you do M over (2m+3) + M over (m+3) ?
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I think what your trying to say has something to do with equations. If you're having trouble on that problem, sheck out the equations.
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Is there a name for the answer you get when you add/subtract fractions?
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what did he say I still don't get it
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it is conufseing me i don't now why
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Why is this so difficult?
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If you work harder, it will be easier.
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16/5 7/5 how do we do this as there is no sign given? it was in my textbook
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i dont understand nothing!!!!
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hi(:
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Bye :(
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what should i do if my fraction is 9/11+6/10
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hi i really dont get adding fraction like i wonder if u can help me
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is there any way to do it without changing the denominators?
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I usually forget how to add them does anybody have any tips for me?
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Multiply the prime by the composite and that can be used as your common denominator
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This looks hard can some one help?
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Thank's! I got it down now !
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i am in 4th grade and i loved the way u teach in a simplified manner.
where can i find problems to solve adding fractions with unlike denominators.
thx
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How do you add a fraction and a whole number? Like 34 + 23/12?
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Why would you multiply 34x12/1x12? Wouldn't that still just be 34?
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thanks so much, now i can understand it much better! I just wanted to ask, what if one of the denominaters is a prime number?
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true that
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I don't understand. This just confuses me. Can anyone turn this video into something that a 13 yr. old can understand?
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well me too, but I'll be 13 next month. Well, we'll have to understand it sooner or later...
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this stuff is easy it is getting close to FCAT i am ready
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hi this was REALY helpfull thnx!
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yea ur rite..... XD
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I still don't get it
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Do you have to simplify both fractions before finding the common denominator?
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how do u add and subtracted fractions
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When you find a common denominator are you allowed to divide instead of multiply 9x2=18 ,9x3=27and blah blah blah ?
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Is there any other faster ways to do the problems instead of just wasting so much time on only one problem when i could be on the next one in just a minute or less?
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Guys Mr. Khan is a smart guy and this is a learning program. What if somebody asks you to add fractions and you do the LCM way and get it wrong? what happens then?
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can you please show hard and not easy like 9 and 12 ha s denominator and some thing like 7 and 8
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thanks
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can you please teach me calculus ?
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That's in the calculus section.
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But what if you get a improper fraction do you have to turn it into a mixed number or can you just let it be.
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If your asked to "simplify" the answer, turn it into an improper fraction. Other than that, it depends on whether or not your teacher wants you to.
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What do I do to make the answer positive?
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Can u multiply it with a bigger denominater ?
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Sure, you can use any denominator you want, as long as they are common. Then reduce at the end for the last step. Tip: See the recognizing divisibility video. It is very helpful.
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How do you reduce
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Try finding numbers that go into both numbers.

24 and 9 are both divisible by 3 so if a fraction looked like

9/24

you could reduce it to

3/8
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where are the problem exercises?
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why did people invent fractions there so HARD!
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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.
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excellent video !!!
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tell me the answer to this 56/93 + 43/94
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How do you simplify it if it is not an improper fraction?
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I am lost. can someone explain when you need to simplify the fraction at the beginning or the at the end of the problem?
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When I search for hint. It does not seems well And i Gotta do my math right now. BYE EVERYONE
BYE ,
FROM
TYLER HALL
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WOW GREAT SEE THE VIDEO
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When subtracting mixed fractions, what if the second fraction is larger than the first? Like 7 3/5 - 5 4/5 = ?
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what is sals email
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where are the practice problems?
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why at 1:48 do u do 4x4
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Okay so this is today's homework is about that and I haven't really get what I had to do so look at this problem 1/3 + 5/9 they both can't reduce! or unless you can do the factor tree on 1 and 3 okay never mind thank you for doing this video I really didn't understand Adding Fractions with Unlike Denominators. and plus is their ever gonna be a problem with dividing? Like with unlike denominators?
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is there also ever gonna be a unequal problem?
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Is there another way that you can do this process?
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this video has helped me like sooooooooo much. THANKS SAL!
ttyl
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no prob!!!!!!!!!!!!!!
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What if i have two denominators that don't divide into any number equally, like nine and eleven?
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Thanks for the video but I was sort of confused with how you got the 3.
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thax f4 the help
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can you show an ex. of m-5 over m squared+9m+20 +4m-1 over m squared +7m+10 ?
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At 1:29 Sal says three, even though he meant four.
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Why do the denominators have to be the same?
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still difficult thanks sal :[
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It took me forever to get this. I think I did over 200 problems on the moduel before I was concidered "proficient". Whew, all done.....now....*leaps* to tackle Algebra 1 *pounces on Algebra 1*
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=]? :) ;)

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what are "signs" in adding fractions with different signs
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/, x, -, and + are all different signs. Is that what you meant?
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thank you i get it now
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i am not trying to be mean but thats a comment:)
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doesn't MR.khan have a other way of of adding and subtracting fractions like the birthday cake method
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Don't know, good question, maybe you can ask Mr. Khan yourself and see if he does have another method.
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Why are both the denominators the same?
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If you want to add or subtract a fraction, you have to make both side have the same denominator.
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Starting from 3:19 until 3:23, Sal says 9 even though he meant 49.
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(THIS IS A COMMENT NO A QUESTION)
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Is there an easier way to learn this im having a very hard time getting this in my head Thanks in advance
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So how would you do a question like 1/4 - 3/12 ?
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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!
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how do you order fractions

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what is common denominator in 6/7 + 8/21
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How would you do 4-6/5?
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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
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how did you know to multiply in the begging of the video
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need help with trying to find the lcd of 3/55+9/77
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Make a video that tells me how to simplify a fraction that is NOT an improper fraction!
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is there adding and subtracting negative fractions with unlike denominators?????i need feedback
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yes find it
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how do i get the answer whne one od the fractions is negatice e.g -3/5 +1/2 ??
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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
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i don't know how to make the fraction simple
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Report a mistake in the video
Example:

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

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