字幕表 動画を再生する
-
- [Instructor] So they are telling us that
-
r fifths is equal to eight tenths
-
and we need to figure out what is r going to be equal to
-
and they help us out with this number line
-
where they've put eight tenths on the number line.
-
That makes sense because to go from zero to one,
-
they've split it into one, two, three, four,
-
five, six, seven, eight, nine, ten equal jumps
-
and at this point, we have gone eight of those ten
-
equal jumps between zero and one so that is eight tenths
-
and they've also labeled one fifth for us
-
and one way to think about it is
-
if we look at these bold lines,
-
zero,
-
one,
-
two,
-
three,
-
four,
-
five,
-
if you just look at the purple, we have five equal jumps.
-
So each of those jumps are a fifth
-
and so it makes sense that our first jump
-
right over here gets us to one fifth
-
and you can see that
-
that is equivalent to two of the tenths.
-
I'll just write that up here so we can see that equivalence.
-
One fifth is equal to two tenths
-
but how many fifths is equal to eight tenths?
-
Pause this video and try to figure it out.
-
All right, well this is one fifth.
-
If we do one more jump of a fifth, that would be two fifths.
-
Then if we go another fifth,
-
that will get us to three fifths
-
and then if we go another fifth,
-
that will get us to four fifths
-
which we see is exactly equivalent to eight tenths
-
and that makes sense because we also saw that
-
every fifth is equivalent to two tenths.
-
So four fifths is going to be equivalent
-
to eight of those tenths.
-
We see that very clearly right over here
-
and so r is equal to four.
-
Four fifths is equal to eight tenths.
-
So r is equal to four.
-
Let's do another example.
-
What fraction is equivalent to point A?
-
So pause this video and see if you can figure that out.
-
All right, so let's figure out where point A is.
-
So to go from zero to one,
-
we have one, two, three, four, five, six equal jumps.
-
So each of these jumps are a sixth.
-
So going from zero, one jump will get us to one sixth,
-
then two sixths, then three sixths,
-
then four sixths, then five sixths
-
and so can we see four sixths in the choices?
-
No I do not see four sixths.
-
So we have to find an equivalent fraction to four sixths.
-
So we could go choice by choice.
-
The first choice has five sixths.
-
Well we very clearly see that five sixths
-
would be here on the number line
-
which is clearly a different place than four sixths.
-
So we could rule out this first choice
-
but what about these other ones?
-
Let's see, let's see how we can think about.
-
Four fifths versus four sixths.
-
Could those be equivalent?
-
If I have four out of five versus four out of six,
-
that's not feeling too good
-
so I'm gonna put like a curly line through it.
-
That's not feeling right, that if I could have
-
four out of five equal jumps or five equal sections,
-
that that would be the same
-
as four out of six equal sections.
-
If I divided it into six equal sections,
-
each of those sections are going to be a little bit
-
smaller than if I divided into five equal sections.
-
So if I have four of each,
-
they're going to be a different value.
-
Actually when I talk it out like that,
-
I feel even more confident that I could rule this one out.
-
Now what about six fourths?
-
Well one way to think about it
-
is four fourths would be equal to one.
-
So six fourths is going to be beyond one.
-
So it's definitely not going to be where A is,
-
so I could rule that one out
-
and we could say oh, well maybe it's just going to be D
-
but let's make sure that this makes sense.
-
Two thirds, what does two thirds look like?
-
Well let me try to divide this part of the number line
-
from zero to one into thirds, into three equal sections.
-
So I have zero there
-
and then that could be one third,
-
two thirds and then three thirds.
-
That looks like three equal sections.
-
So this is one third,
-
this is two thirds, I'm making another jump of a third
-
and then when I get to one, of course that is three thirds
-
or we could have said six sixths
-
and so point A,
-
which is right over here I'm writing over it,
-
that is indeed equal to two thirds.
-
You can see each jump of a third is equal to two sixths.
-
So it makes sense that four sixths is equal to two thirds
-
or that two thirds is equal to four sixths
-
so I like this one.