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Course: Arithmetic>Unit 13

Lesson 6: Adding and subtracting fractions with unlike denominators word problems

Learn how to add and subtract fractions with unlike denominators through a real-world problem. Watch as the problem is broken down step-by-step, practice finding common denominators, and apply this knowledge to determine if the sum or difference of the fractions meets a specific requirement. Created by Sal Khan.

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• This is very good and has helped me a lot on math.....

I bet this comment cant get 10 upvotes
• question when looking for a common denominator
must it be the lowest you can find or can it be just any?
• A common denominator cannot be "any" number, because it has to fit both fractions. However, it can be "any" fitting number. The reason you want it to be a smaller number is that it makes adding and simplifying easier. (see simplifying fractions) I hope this helped!
• you are confusing me about splitting the bar graph
• Splitting the bar graph really isn't at all confusing.It means that you divide something into fractions so you can understand better.The best object to use is a bar graph.Sal divided the first two into different fractions.Then, when you converted the two into fractions with same denominators,you add them together.When you add it,you get the answer,which Sal demonstrated in the third bar graph. So it is not confusing at all.Thanks for reading this reply!
• thank u for helping me i think ima get a 100
• Hope you do
• if you are confused in this vid comment
• If you are watching all the videos and taking all the tests and quizzes you must be able to get comfy w these. Don't forget to work hard and be patient.
• Sometimes math can be soooo hard.
• ok so i dont know how to divide
and im really bad at math
• If you try your best, you'll get better! :)
• I need help with EVERYTHING
• if i am to subtract two fraction and one of the denominator is missing, how do you work it out.
• It first depends what other information that you have. If you have the answer, you might be able to work out the problem by taking the largest and smallest fractions and subtracting them from each other. Also, if there is subtracting going on with a common denominator, you may be able to subtract them.