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### Course: Class 5>Unit 3

Lesson 4: Adding or subtracting unlike fractions

# Adding fractions with unlike denominators

Learn how to add two fractions with different denominators. It can be challenging to combine fractions when the denominators don't match. It is important to find a common denominator. Finally, the resource shows how to find a common multiple of the two denominators in order to convert the fractions so they can be added together.

## Want to join the conversation?

• How do I find the common denominator for 3/4+3/8??
• First, you'll want to figure out whether or not the larger denominator (3/8) is divisible by the smaller one (3/4). In this case, the 8 is divisible by 4, (8/4 = 2), so you're going to multiply the smaller one (4) by 2, bringing it to 8. Now, you have to remember, whenever you scale fractions, you have to multiply both, so now it's 6/8+3/8 = 9/8 = 1 1/8. In other cases where the larger denominator isn't divisible by the smaller one, find the LCM (least/smallest common multiple), and scale both fractions so the denominators are equal. Hope this helped!
• khan academy needs to add dark mode for people who spend along time on their website because your eyes are gonna start to hurt. *UPVOTE IF YOU AGREE LETS START A PETITION TOGETHER!*
• the white is the theme for the website because it most likely is used to catch teachers or schools eyes and they will see that its used for learning and the website will be used more [my theory for this]
• Can the Rule of Four be used for what he teaches at ? Or is this something different?
• yes it can
• Play it at speed 0.25. Upvote if you tried :D
• I tried 1.25
(1 vote)
• At to . Since Sal says that 9/10 and 27/10 are the same number, could you have written only 9/10 or 27/30.
• Good Question! You can do it either ways! But sal is not switching the numbers in this video! You could do both but only can do 27/30 when switching numbers!
• I do not understand what if it is a whole number times a fraction
• If there is a whole number, you would make the whole number look like this: (this is just an example) 3/1. If the whole number is 3, then you just make the whole number over one. 3/1.
I hope this helped you!!

P.S. Sorry for the three-year-late response!!
• I don't understand what he did in , someone please explain
• the fraction was a improper fraction so he made it a proper fraction by saying 15 goes into 16 1 time and there's a re
remainder of 1
• How do you make fractions into decimals.