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Lesson 4: Adding and subtracting mixed numbers with unlike denominators

# Adding mixed numbers: 19 3/18 + 18 2/3

To add two mixed numbers, you can separate the whole number and fraction parts. Add the whole numbers together as you normally would, and then find a common denominator to add the fractions. Once you have your sum, you may need to simplify the fraction for your final answer. Created by Sal Khan.

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• Why can't I convert the mixed numbers into improper fractions and then add them together? • I don't get this. Help! • How come we can’t just add it like a regular adding problem? • I know what to do now! Thanks for the video to help me! Merry Christmas!! 🎄⛄ • Let's add 19 and 3/18 to 18 and 2/3. So I like to separate out the whole number parts from the fraction parts. So 19 and 3/18 is the same thing as 19 plus 3/18. And to that, we are going to add 18 and 2/3, which is the same thing as 18 plus 2/3. Now we can separately add the whole number parts. So we could add the 19 to the 18. So we could do 19 plus 18. And then we can add the fraction parts-- let me do this in green-- plus 3/18 plus 2/3. Now 19/18, pretty straightforward. That is what? Let's see. 19 plus 19 would be 38. So this is going to be 1 less than that. It's going to be 37. So that gives me 37. And then 3/18 plus 2/3, to add them, I need to have the same denominator. And the least common multiple of 18 and 3 is 18. So let's convert 2/3 to something over 18. So 2/3, if I want to write it as something over 18, well, I multiplied the denominator by 6, so I'd also have to multiply the numerator by 6. So it's the same thing as 12/18. So I can rewrite 2/3 as 12/18. And now I can add these two things together. That's going to be-- so I have 37 plus-- it's going to be something over 18-- plus something over 18. 3 plus 12 is 15, plus 15/18. And so expressing this as a mixed number, I get 37 and 15/18. And that's the right number. But we can simplify it even more. We can simplify the 15/18. Both the numerator and the denominator are divisible by 3. So let's divide them both by 3. And we're not changing the value because we're doing the same thing to the numerator and the denominator. And so this gives us, we still have our 37, but the numerator is now 5, and the denominator is now 6. So we get 37 and 5/6. And we're done.
• I don't get it like WHAT • wut dont u get its pretty straight forward foe exm. if u wanted to find lets say 1 1/2 + 2 6/8
u would covert the mixed number into an improper fraction so the first number would be 1 1/2 u would take the 2 and times it by the whole number which is the big 1 then u would add the 1 thats above the 2 and get 3/2 for the second number u would do the same thing and should get 22/8 then u see we have unlike denominators so wut times 2 would get u to 8 it would be 4 so u muliply 3/2 x 4/4 and get 12/8 then u add! and ta dah!!UwU
(1 vote)
1.you need to find a common denominator if the denominator for both of the fractions is not the same
Steps to find out common denominator:
ex: 4/49+3/7 - 49 is a multiple of 7 , to get 49 you multiply 7x7
2.now all you have to do is multiply 4x7 which gives you 28
so then your fraction will become 28/49+3/7
3.then you just add the numerator

I hope this helps! • are there tricks to simplifying odd fractions? • (⌐▀͡ ̯ʖ▀)=/̵͇̿̿/'̿'̿̿̿ ̿ ̿̿   