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## 4th grade

### Course: 4th grade > Unit 7

Lesson 4: Comparing fractions with unlike denominators# Comparing fractions word problems

Sal practices comparing fractions using real-world contexts.

## Want to join the conversation?

- HOW does he draw so good on the computer(18 votes)
- I don't know, its just depends on his skills(3 votes)

- Like my comment if you think Khan Academy is the best(17 votes)
- i understand this way but is there any easy way to find it ? coz i cant draw the box and compare it like this ?

i use this method to compare more no's , if it is unlike denominators i used to convert all into one deno by doing LCM but i cant use this method here .(11 votes)- you can think about equivalent fractions(5 votes)

- how is he so good at drawing and teaching on the computer(9 votes)
- Well... you can't actually draw these fractions they don't fit into the same sized strip so making them look like they do isn't accurate, really to draw fractions they have to be equivalent because they have to be equal pieces and fit into the same sized strip to accurately compare them all together.

You can compare 7/8 and 3/4 together and 3/6 and 2/3 together but you can't actually do anything with 5/10 i'm not sure how you make it look like it does but it doesn't. All of these fractions in the video only share 1 Common Multiple too which is 120 (i just ran an LCM Calculator on it because seemingly they didn't share any).

So i guess if you used Least Common Multiple you'd have to keep writing the multiples for each Denominator until you see at least 1 Common Multiple, that's just 1 way to figure these out anyway when we get several fractions where half ARE equivalent and then the other half aren't. That's what's making them harder comparing 3 or more fractions, before for 2 fractions we were using all equivalent fractions.

You can also change them to a decimal number which honestly is far easier, if you're at school they may not let you do that but it's the quickest solution for comparing several fractions.(8 votes) - i love these questions they are so fun(7 votes)
- math and reading(6 votes)
- Im in 3rd grade doing 4th grade math im smart.(3 votes)

- this is good practice to get ready(6 votes)
- How do you multiply fractions with unlike denominators?(5 votes)

## Video transcript

- [Instructor] We're told
that Katie made a table to show how much time she
spent on homework last week, and so we can see the different subjects and then how much she
spent in terms of hours. So in math, she spent 3/4 of an hour, reading, 7/8 of an hour, writing, 3/6 of an hour, and then science, 5/10 of an hour. And then they ask us on which activities did Katie spend more than 2/3 of an hour? So pause this video and see
if you can figure that out. All right, so we essentially
have to figure out which of these fractions are
greater than 2/3 of an hour? Which are greater than 2/3? And this is all in terms of hours. So first let's just think
about representing 2/3, so let me do it like this, and I'm going to hand draw it so it's not going to be perfect. But if this is a whole right over here, I could split it into
three equal sections, so I'm gonna try to do that. Let me see, does that look about right? So three equal sections, so that would be 1/3 that would be 1/3, and then that would be 1/3, and then 2/3 would be two of them, so I'll pick these first two. Well, it doesn't have
to be those first two, so that's 1/3 and then 2/3. So let's see if we can
draw a similar visual for each of these. So what about 3/4? So once again, let's make this a whole. And now if I want to
think in terms of fourths, I have to divide it into
four equal sections, so let's see. If I divide it, that will
be two equal sections, and then I can divide each of those into two equal sections, so let's see. Maybe something like this, and then like this. So it's hand drawn, but these
are four equal sections, and so this would be a fourth, that would be a fourth,
and that would be a fourth, and that would be a fourth. 4/4 make a whole, so three of those fourths would be one, two, and then three. And so you can see, and
I've drawn it pretty close. It's not perfect 'cause it's hand drawn, but you can see that 3/4 is
more of a whole than 2/3. It's greater than 2/3. So Katie spent more than
2/3 of an hour on math because 3/4 is greater than 2/3, so I like this one right over there. I'll just put a square
or circle around the ones that she spent that extra time on or the more, the greater
than 2/3 of an hour on. And I'll think about reading, 7/8. So to compare that, I will, once again, make a whole here, and then I want to think about 7/8, so I'm gonna split into
eight equal sections. So let's see, that will split
into two equal sections, and then, then I can go
to four equal sections, and then if I split
each of those into two, this would be eight equal sections, so it may look something like this. Not perfect, but I think
it will get the job done. So each of these are 1/8, so 7/8 are going to be one, two, three, four, five, six, and 7/8. Clearly, once again, greater than our 2/3
that we have in purple. So she spent more than
2/3 of an hour on reading. Now what about writing? 3/6, what would that look like? Well, I'll do another one right over here. So if that is a whole, well, actually let me
split it to thirds first, since we already have a
bit of a reference there. We can look up there and we can see. Those are thirds and if we
split each of those into two, we're going to have sixths, 'cause we'll have six equal sections. So it would look something like that, and then three of those six, well, that's one, two, and three. So we can see that 3/6 is less than 2/3 so I'm not gonna circle that one. She didn't spend more than
2/3 of an hour on writing, and then last, but not least, science. 5/10. Well once again, we could make a whole here, and let's see. I want to do into 10 equal sections, so that's two equal sections, and each of these, I can do
into five equal sections. Let's see. One, two, three, four, five, I can do a
little bit neater than that, three, four and five, and then one, two, three, four and five. I can make it a little bit neater, but I think this will get us to where we need to get to. So these are each 1/10. I could write 1/10, 1/10, I could do that for all 10 of these, but we care about five of these tenths, so one, two, three, four, five of those tenths. And notice, 5/10 is the
exact same thing as 3/6, and like 3/6, it is less than 2/3. So which activities did
Katie spend more than 2/3 of an hour on? Clearly, math and reading.