Decomposing a fraction visually | Fractions | Pre-Algebra | Khan Academy

Decomposing a fraction visually | Fractions | Pre-Algebra | Khan Academy


So let’s think about all
of the different ways that we can represent 7/9. So let’s just visualize 7/9. So here I have 9 equal sections. And 7/9 you could represent
as 7 of those equal sections. So let me get myself a
bigger thing to draw with, so that I can fill this in fast. Actually, I don’t
like how that looks. I’m going to use
the paint brush. So here we go. So that’s 1, 2, 3,
4– you know where this is going– 5, 6, and 7. So that’s one way
of representing 7/9. We already know that. That’s not too interesting. But let’s see if we
can represent 7/9 as the sum of other fractions. So let’s imagine maybe
we can represent it as– let’s do it as 2/9. Let me use a
different brush here. So let’s represent it as 2/9. 2/9 plus– I don’t know,
let’s see, maybe 3/9. But that doesn’t quite
get us to 7/9 yet. 2/9 plus 3/9 is going
to get us to 5/9. So we’re going to need 2 more. So it’s going to be
plus another 2/9. So what would this look like? So let’s just draw
another grid here. So this is going to
look like– and I’ll try to do it right
below it, so that we can see how they match up. So we have 2/9, this
2/9 right over here. Well, we have each
of these as a ninth. We have 9 equal sections. So we’re going to get 1 and 2. And then we’re going
to add 3 more ninths. So 1, 2, 3. So we add 3/9 right over
there and then 2 more ninths, 1 and 2. So notice, when I added 2/9 to
3/9 to 2/9, this equals 7/9. And we know that when we
add a bunch of fractions like this that have
the same denominator, we can just add the numerator. And this is why. This is 2/9 plus 3/9 times
2/9 is going to give me 7/9. Let’s do this one more time. This is actually a lot of fun. So let me draw my grid again. And then let’s see
what we can do. So let me get my pen tool out. Let me make sure my
ink isn’t too thick. Well, this is fine. And let’s add a
couple of ninths here. So let’s add first 1/9. And I’m going to draw
out all the 9’s in blue. And let’s add 2/9. And then we could add– I don’t
know, maybe we could add– let me give some space here
so we can add more. And maybe we could add 3/9. And then we could add, let’s
see– actually, let me just write this out. I’m going to try to add
four fractions here. So let’s say add first 1/9
and see where that gets us. So 1/9 is going to get
us right over here. So that’s 1/9. So let’s say we add 2/9 to that. I’ve got my little
paint brush going on. So that’s 1 and 2 more, 2/9. So that still
doesn’t get us there. This gives us a total of 3/9. 1 plus 2 is 3– 3/9. So let’s add 4/9. And I’ll do that
in this blue color. So 4/9. That’s different enough. So let’s see where this gets us. Actually, well, why not? So 4/9. And so that’s going
to get us 1, 2, 3, 4. So that looks like it
got us all the way, because 1 plus 2 plus 4 is
going to give us 7– 7/9. So what could we put here? Well, we could say 0/9. Why not? So we could call this
one right over here 0/9. And how would we visualize that? Well, we’re saying
none of these. No ninths right over here. So this is 1/9 plus 2/9
plus 4/9 is equal to 7/9. So these are all different
ways to decompose the exact same fraction.

14 thoughts on “Decomposing a fraction visually | Fractions | Pre-Algebra | Khan Academy

  • August 20, 2013 at 6:06 pm
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    Thank you for all the effort you put into these videos and your website!
    Have a nice day

    Reply
  • September 22, 2014 at 7:18 pm
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    u sk dk

    Reply
  • November 20, 2014 at 2:30 am
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    Thanks so much, I don't know what I'd do without these videos.

    Reply
  • November 5, 2015 at 3:24 pm
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    that really helped thanks

    Reply
  • January 26, 2016 at 11:59 pm
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    I get it thx

    Reply
  • March 19, 2016 at 9:18 pm
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    thank you before I didn't know what the heck a decompose fraction was.

    Reply
  • November 3, 2016 at 12:52 am
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    thank you so so so much you help me with my home work and it's fun

    Reply
  • October 22, 2017 at 4:13 pm
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    rlly? ur kidding me. Do some Roblox vids.

    Reply
  • December 6, 2017 at 10:36 pm
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    Thanks just helped my son with homework and understood it.

    Reply
  • January 31, 2018 at 12:20 am
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    Thank you so much my teacher recommends these videos

    Reply
  • February 7, 2018 at 9:38 pm
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    Mmm k

    Reply
  • September 14, 2018 at 1:09 am
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    Omg I can understand thanks so much

    Reply
  • February 1, 2020 at 12:54 am
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    How is this asmr to me?

    Reply
  • February 3, 2020 at 10:18 pm
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    WOW! I like how you used different colors to visualize the different fractions just one question can you add 4/9+3/9=7/9? Would that be called decomposing fraction?

    Reply

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