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  • - [Instructor] So what we're going to do in this video

  • is think about equivalent fractions.

  • So let's say we have the fraction 3/4,

  • and I wanna think about

  • what is an equivalent number of eighths?

  • So 3/4 is equal to how many eighths?

  • And to represent that how many,

  • I could put a question mark there,

  • but instead of a question mark, I'll just put a letter.

  • So what should y be?

  • 3/4 is equal to y/8.

  • What does y need to be to make this true?

  • And before I tell you go go pause this video

  • and try to work on it on your own,

  • which I will do in a little bit,

  • I'll give you a little bit of a hint.

  • So let's try to represent 3/4, or I'll represent it for you.

  • So I will do it with this rectangle.

  • So I'm going to divide it into four equal sections.

  • So let's see, that would be dividing it roughly in half.

  • I'm hand-drawing it, so it's not perfect,

  • but these should be equal sections.

  • The areas of each of these sections should be equal.

  • So there you go, this is my hand-drawn version of that.

  • And so three of those four, and I will do that in purple.

  • Three of those four, it could be one,

  • two, and then just for kicks I will do this one out here.

  • So that is 3/4 right over there.

  • So if I were to think about this in terms of eighths.

  • So I'm going to draw another whole.

  • But this time instead of just splitting them into fourths,

  • I'm going to split it into eighths.

  • So let's do the fourths first,

  • just 'cause it's easy to look at the one above that.

  • So that's my fourths.

  • And then I'll divide each of the fourths into two.

  • So that gives me eighths.

  • All right, almost there.

  • The drawing is really the hardest part here.

  • And so each of these is an eighth.

  • It's hand-drawn.

  • But imagine if there were eight equal sections.

  • So how many eighths is equal to 3/4?

  • Pause the video and try to work it out on your own.

  • All right, well, we can just look at this visually.

  • So this first fourth, we could say that's equivalent

  • to filling out this eighth and this eighth.

  • So that first fourth is equal to 2/8.

  • This second fourth is equal

  • to another two of these eighths.

  • And then this third fourth is equal

  • to another two of the eighths.

  • So how many eighths have I shaded in?

  • Well, I have one, two, three, four, five, 6/8.

  • So I have six over eight.

  • So 3/4 is equivalent to 6/8.

  • So in this scenario, y is equal to 6/8,

  • or we could say 6/8 is equal to y.

  • Now let's do another example.

  • So what we could see here in this top circle

  • is we've divided it into six equal sections.

  • So each of these are one of the six equal sections or 1/6.

  • And we can see that one, two, three, four

  • of them are shaded in.

  • So what we have represented in that top circle,

  • that is four out of six.

  • So what I wanna think about is

  • how many thirds are equivalent to 4/6?

  • Pause this video and think about it.

  • So once again, how many thirds are equivalent to 4/6?

  • Instead of just putting a question mark there,

  • I'll put the letter x.

  • So what should x be for these two things to be equivalent?

  • Or another way to think about it is

  • four over six is equal to

  • x over three.

  • 4/6 is equal to how many thirds?

  • All right, now let's do this together.

  • And so one way you could think about it,

  • let's see, for 1/3,

  • for us to make this equal to 1/3,

  • it looks like that is equivalent to

  • what I am circling in the orange up here.

  • And that also makes sense.

  • If I were to divided 1/3 into two,

  • so now I would have this would be 1/6 and that would be 1/6.

  • So you need 2/6 to make up 1/3,

  • or each 1/3 is equivalent to 2/6.

  • So this is 1/3 right over here.

  • And that is equivalent to two of these sixths.

  • But we are not completely done yet.

  • We have another two sixths.

  • So we could say those two sixths are equivalent

  • to another third.

  • And it's a little tricky because they didn't put

  • this sixth next to that sixth,

  • but you could imagine if we were to move.

  • Let's say we were to move this sixth.

  • So I'm gonna color this one in white.

  • So if I were to move that sixth to right over here.

  • So we're shading this one in instead.

  • So then you can see that these two sixths right over here,

  • these two sixths are equivalent

  • to this third right over there.

  • So what you can see is, is that our 4/6,

  • and remember, I moved this one over,

  • so I'm not shading this one in anymore.

  • But you can see the 4/6

  • that I've shaded in is equivalent to 2/3.

  • Or another way to say it is x would be equal to two.

  • X would be equal to two.

  • 4/6 is equal to x/3, or 4/6 is equal to 2/3.

- [Instructor] So what we're going to do in this video

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A2 初級

有模型的等效分數 (Equivalent fractions with models)

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    林宜悉 發佈於 2021 年 01 月 14 日
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