Main content

## 5th grade foundations (Eureka Math/EngageNY)

### Unit 3: Lesson 3

Topic C: Foundations- Intro to adding mixed numbers
- Intro to subtracting mixed numbers
- Add and subtract mixed numbers (with regrouping)
- Comparing fractions: tape diagram
- Comparing fractions: number line
- Visually compare fractions with unlike denominators
- Visually comparing fractions review

© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice

# Intro to adding mixed numbers

Sal adds 2 mixed numbers with common (like) denominators.

## Want to join the conversation?

- Will it make sense if you convert those mixed numbers to improper fractions then convert it back again to mixed numbers to get also the same correct answer?

Example:

(Convert to improper fraction)

2 4/7 = 18/7

3 2/7 = 23/7

(Add both improper fractions)

18/7 + 23/7 = 41/7

(Convert back to mixed number)

7÷41 = 5r6

= 5 6/7

Same with:

2 4/7 + 3 2/7 = 5 6/7(17 votes)- Yes, this makes sense! I actually think that it's easier to convert to improper fractions before adding / subtracting / etc. As long as you watch your math when you are converting back and forth, you should have no problem!(9 votes)

- what is the easiest way to add fractions(5 votes)
- Make both fractions an improper fraction and then add them. I hope this helped! (Sorry if it doesn’t)(9 votes)

- what happens if the answer is improper(5 votes)
- it would say : your answer is almost correct but it needs to be simplified(5 votes)

- How do you do 5 6/8+8 5/6?(5 votes)
- First, you would add the fractions:

6/8 + 5/6

To do this, you have to find their common denominator:

What is the least common multiple of the denominators, 6 and 8? 24.

Then, you make the fractions equivalent with the same denominator.

if 5/6 had to become x/24, what would x equal? Well, what is 6 being multiplied by to make 24? 4. Whenever you multiply the denominator by something (in this case, 4) you also have to multiply the numerator. In this case, 5/6 would equal 20/24, which is equivalent.

You do the same thing for 6/8:

It becomes (6*3)/24, which equals 18/24.

P.S. To check this, you can always simplify your new fraction to make sure it is still equivalent.

Then, you add these fractions together. So:

20/24 + 18/24 = 38/24

This is an improper fraction. So now, you have to convert it to a mixed number. 24 goes into 38 one time with 14 left over. So we get:

1 14/24, or simplified, 1 7/12.

Now we add the whole numbers:

5 + 5 = 10.

Then, we add the mixed number to 10 which makes 11 7/12.

Your final answer is 11 7/12.

Hope that helped.(7 votes)

- i cant hear it please help me somebody(5 votes)
- Try and look at the transcript if that doesn't work ask your teacher to help you (hope this helps)(3 votes)

- Now I understand how to add mixed numbers.👍(7 votes)
- no i don,t understand can someone help me here🥺🥺🥺🥺🥺🥺(6 votes)
- When it comes to step 3 I get confused when you have to put your fraction in "Simplest Form".Is is ok if anybody who know it can explain it in a different way?:3Pwease?(3 votes)
- So the way to get a fraction like 5/3 into a mixed number is you would divide by 3 then you would get a remainder of 2. Then you would put it as 1 2/3 then to check this is multiply 3 by 1 and add 2 and retain the denominator. This will give you 5/3.(7 votes)

- i need to learn subtracting mixed number's(6 votes)
- Why don't you add the denominator?(4 votes)
- because your not adding more parts, you are adding more things. if you add the parts, the answer will never reach 1.(4 votes)

## Video transcript

- [Voiceover] Let's give
ourselves some practice adding mixed numbers. So let's say I want to add
two, let me write it this way. Let's say I want to add
two and four sevenths plus three and two sevenths,
three and two sevenths. I encourage you to pause this video and try to think about
what this is going to be. Well there's a couple of ways
that you could tackle it. One way, you could say, well let me just add the nonfraction parts. You could say that two plus
three is equal to five, and then you could say that
four sevenths plus two sevenths is equal to well four
sevenths plus two sevenths is gonna be equal to six sevenths. Hey, wait, wait, wait, how
did I, how did I do that? How did I just only add the fraction parts or add the whole parts? Well the way I did that is because two and four sevenths is the same thing as two plus four sevenths. Two and four sevenths, same
thing as two plus four sevenths. And then plus three and two
sevenths is the same thing as three plus two sevenths, so all I did over here,
two and four sevenths plus three and two sevenths, is two plus four sevenths
plus three plus two sevenths. And you can swap the
order in how this happens. So you could take, you
could just switch the order and say this is going to be
two plus three, two plus three, plus four sevenths, plus two sevenths. And what we just figured out was that two plus three is equal
to five, right over here, and that four sevenths plus two sevenths is equal to six sevenths, just like that. Now let's do a more interesting example. Let's do, let's say that I
have three and three fifths, three and three fifths
plus five and four fifths. Now what is this going to be equal to? Well if you do the same technique, if you add the three plus the five, you're going to get eight, and then if you add the three
fifths plus four fifths, you would get seven fifths. So you get eight and seven fifths. And this wouldn't be wrong. This is eight and seven fifths, if you add these two things together, but it's a little bit strange here because seven fifths
is bigger than a whole. So to get a better sense of what number's really being represented here, I want to rewrite this. So eight and seven fifths, this is the same thing as eight plus, and instead of seven fifths, we could say this is the
same thing as five fifths, which is a whole, plus two fifths. Now why is that interesting? Because five fifths, notice
five fifths plus two fifths, that's seven fifths right over there. Or you can consider five fifths to be one, so this is eight plus one, which is nine, and two fifths, nine and two fifths. So all I did here, I added it the same way that I did the first
problem a few seconds ago. But when I realize this fraction
part is greater than one, I separated it into
one and then a fraction that is less than one, and that whole, I was able to add to the eight to get to nine, and then I would have
two fifths left over. Eight and seven fifths,
because five fifths is a whole, is the same thing as nine and two fifths. So if I wanted to write this
in, I guess, a clearer way, I would say this is nine and two fifths. Three and three fifths
plus five and four fifths is nine and two fifths, and once again, we say wait,
three plus five is only eight, how did I get a nine? Well that's because three
fifths plus four fifths is greater than one.