## Dividing Fractions

• 0:00 - 0:01
• 0:01 - 0:05
Divide and write the answer
as a mixed number.
• 0:05 - 0:08
And we have 3/5 divided
by 1/2.
• 0:08 - 0:10
Now, whenever you're dividing
any fractions, you just have
• 0:10 - 0:14
to remember that dividing by a
fraction is the same thing as
• 0:14 - 0:17
multiplying by its reciprocal.
• 0:17 - 0:23
So this thing right here is the
same thing as 3/5 times--
• 0:23 - 0:26
so this is our 3/5 right here,
and instead of a division
• 0:26 - 0:28
sign, you want a multiplication
sign, and
• 0:28 - 0:32
instead of a 1/2, you want to
take the reciprocal of 1/2,
• 0:32 - 0:37
which would be 2/1--
so times 2/1.
• 0:37 - 0:40
So dividing by 1/2 is the
exact same thing as
• 0:40 - 0:42
multiplying by 2/1.
• 0:42 - 0:45
And we just do this as a
straightforward multiplication
• 0:45 - 0:46
problem now.
• 0:46 - 0:50
3 times 2 is 6, so our
new numerator is 6.
• 0:50 - 0:53
5 times 1 is 5.
• 0:53 - 0:57
So 3/5 divided by 1/2 as an
improper fraction is 6/5.
• 0:57 - 1:01
Now, they want us to write
it as at mixed number.
• 1:01 - 1:04
So we divide the 5 into
the 6, figure out how
• 1:04 - 1:05
many times it goes.
• 1:05 - 1:08
That'll be the whole number
part of the mixed number.
• 1:08 - 1:10
And then whatever's left over
will be the remaining
• 1:10 - 1:14
numerator over 5.
• 1:14 - 1:18
So what we'll do is
take 5 into 6.
• 1:18 - 1:21
5 goes into 6 one time.
• 1:21 - 1:23
1 times 5 is 5.
• 1:23 - 1:23
Subtract.
• 1:23 - 1:26
You have a remainder of 1.
• 1:26 - 1:34
So 6/5 is equal to one whole,
or 5/5, and 1/5.
• 1:34 - 1:39
• 1:39 - 1:43
This 1 comes from whatever
is left over.
• 1:43 - 1:44
And now we're done!
• 1:44 - 1:47
3/5 divided by 1/2
is 1 and 1/5.
• 1:47 - 1:49
Now, the one thing that's not
obvious is why did this work?
• 1:49 - 1:54
Why is dividing by 1/2 the
same thing as multiplying
• 1:54 - 1:55
essentially by 2.
• 1:55 - 1:57
2/1 is the same thing as 2.
• 1:57 - 2:00
And to do that, I'll do a little
side-- fairly simple--
• 2:00 - 2:04
example, but hopefully, it
gets the point across.
• 2:04 - 2:06
Let me take four objects.
• 2:06 - 2:09
So we have four objects:
one, two, three, four.
• 2:09 - 2:14
So I have four objects, and if
I were to divide into groups
• 2:14 - 2:17
of two, so I want to divide
it into groups of two.
• 2:17 - 2:21
So that is one group of two and
then that is another group
• 2:21 - 2:24
of two, how many groups
do I have?
• 2:24 - 2:27
Well, 4 divided by 2, I have two
groups of two, so that is
• 2:27 - 2:29
equal to 2.
• 2:29 - 2:31
Now, what if I took those
same four objects:
• 2:31 - 2:34
one, two, three, four.
• 2:34 - 2:36
So I'm taking those
same four objects.
• 2:36 - 2:39
Instead of dividing them into
groups of two, I want to
• 2:39 - 2:45
divide them into groups of 1/2,
which means each group
• 2:45 - 2:47
will have half of
an object in it.
• 2:47 - 2:50
So let's say that would be
one group right there.
• 2:50 - 2:52
That is a second group.
• 2:52 - 2:53
That is a third group.
• 2:53 - 2:57
I think you see each group has
half of a circle in it.
• 2:57 - 2:58
That is the fourth.
• 2:58 - 3:00
That's the fifth.
• 3:00 - 3:01
That's the sixth.
• 3:01 - 3:04
That's the seventh, and then
that's the eighth.
• 3:04 - 3:09
You have eight groups of 1/2,
so this is equal to 8.
• 3:09 - 3:13
And notice, now each of the
objects became two groups.
• 3:13 - 3:15
So you could say how many
groups do you have?
• 3:15 - 3:17
Well, you have four objects
and each of
• 3:17 - 3:21
them became two groups.
• 3:21 - 3:22
I'm looking for a
different color.
• 3:22 - 3:25
Each of them became
two groups, and so
• 3:25 - 3:27
you also have eight.
• 3:27 - 3:31
So dividing by 1/2 is the same
thing as multiplying by 2.
• 3:31 - 3:32
And you could think about it
with other numbers, but
• 3:32 - 3:35
hopefully, that gives you a
little bit of an intuition.
• 3:35 - 3:35
Title:
Dividing Fractions
Description:

U02_L2_T3_we2 Dividing Fractions

more » « less
Video Language:
English
Duration:
03:36
 brettle edited английски език subtitles for Dividing Fractions brettle edited английски език subtitles for Dividing Fractions brettle edited английски език subtitles for Dividing Fractions

Incomplete

• brettle