Dividing Fractions - Free Educational videos for Students in K-12

Dividing Fractions - By tecmath

Transcript


00:0-1	get a welcome to the Tech Math channel . What
00:02	we're going to be having a look at this video
00:03	is dividing fractions and it's a pretty simple thing to
00:06	do , but I'm going to start this one a
00:07	little bit differently to how you may have are seen
00:10	how to divide fractions in the past because I think
00:13	a lot of those videos miss the actual idea why
00:16	we do certain things . So I'm gonna start out
00:18	by not using fractions at all . I'm going to
00:20	start out by using just whole numbers and I'll give
00:23	you this example sales to go six divided by two
00:27	. Now , obviously you probably understand that this means
00:30	how many twos are in six or if we get
00:33	six are breaking into two groups , How big is
00:36	each member of that group ? And that's what six
00:38	divided by two means . We can also think about
00:41	this in terms of our super corn . I'll tell
00:43	you what I mean by that . We can also
00:45	think about this is what is six times a half
00:48	or I'll say this in a different way . What
00:50	is a half of six ? Half of six is
00:53	exactly the same as what is six divided by two
00:56	? You can probably notice the relationship here . Uh
00:59	Pretty much too and a half . Well these are
01:02	the reciprocal one , another that is to say we
01:05	basically are putting one over this number . We're flipping
01:09	this as a fraction upside down because too as a
01:11	fraction is to over one . And the reciprocal that
01:14	is where we flip it upside down and we end
01:17	up with a half . So another way of dividing
01:20	by a fraction or divided by number is multiplying by
01:24	it's reciprocal . I'll give you another example here .
01:27	So say for example where we were looking at 12
01:32	Divided by four . Okay , how many fours are
01:35	in 12 ? Again ? We're using that same idea
01:38	I could say okay well what is a quarter of
01:41	12 ? Okay , the reciprocal of four , which
01:44	is 4/1 is 1/4 . What is a quarter of
01:48	12 ? And we get the same answer . That
01:50	answer of three . So we can use this idea
01:54	with fractions . Say for example I was asking you
01:58	okay what is six divided by one half ? Okay
02:05	, so how many halves are in six and you
02:07	can probably draw this out and work this out ,
02:08	You know ? You could think okay one , There
02:11	is two half . So this answer is going to
02:13	be 12 . But using just a method here that
02:17	we could use to work out all fractions , I'll
02:19	show you . So this reciprocal method , okay ,
02:22	so what is the reciprocal of Half ? And you
02:25	can say okay , the reciprocal of this is this
02:28	fraction turned upside down ? It becomes to over one
02:31	that is the reciprocal of a half . And we're
02:33	going to multiply by that to six Times to over
02:37	one . Well this is equal to 12/1 which is
02:41	equal to 12 . Okay so there's a bit of
02:44	a method there . What we do we're dividing by
02:47	any fraction is we turn it into the reciprocal and
02:50	we multiply it and that's why we do it because
02:53	it's exactly the same thing . Another example here say
02:56	I was going okay what's two thirds ? And this
03:00	is divided by 4/9 ? Well now the numbers are
03:03	a little bit scary right ? But we do exactly
03:07	that same thing . We're going to work out the
03:08	reciprocal of this number here and multiply it . So
03:12	we're going to keep the two thirds . But we're
03:14	going to multiply by this four . Nineths reciprocal ,
03:17	we're gonna flip it . This is going to become
03:19	9/4 , Okay , two times nine is equal to
03:25	18 , 3 times four is equal to 12 .
03:28	We can simplify this . Uh six goes into both
03:32	of these , this becomes 3/2 and then we can
03:35	turn it into a mixed number . Three , divided
03:38	by two is 1.5 . I hope you get that
03:42	idea . I can I want to go through another
03:44	example here . What about actually I'll write up a
03:46	couple of examples that you can do . Okay ,
03:48	what is for divided by a third ? Okay what
03:53	is a half divided by six ? What about what
03:58	is 2/7 divided by 3/4 And I think we're gonna
04:05	run our room , let's just give it a fly
04:07	Anyway let's say what is 1.5 divided by two and
04:12	a quarter . That's about as nasty as you'll get
04:15	. Okay four questions there , you should be able
04:18	to solve them . Just remember first off , you're
04:20	going to find the reciprocal of the second number that
04:22	is to say you're going to flip it and then
04:25	you're going to multiply . Okay , so let's do
04:27	this . Okay , so four divided by a third
04:30	becomes for multiply by the reciprocal of the third ,
04:34	which is 3/1 , this is 4/1 4/1 times 3/1
04:40	is equal to 12 . Okay , half divided by
04:45	six . So this becomes a half multiply by the
04:49	reciprocal of six . Remember six is 6/1 , so
04:52	this becomes 1/6 . Alright , one times one is
04:56	equal to 12 times six is equal to 12 ,
05:02	2/7 divided by three quarters , we keep it to
05:05	seventh the same and we are going to work out
05:08	the reciprocal of three quarters The reciprocal when we flip
05:11	this becomes four divided by three . Two times four
05:16	is equal to 87 times three is equal to 21
05:21	. And we can't simplify that any further . Last
05:24	of all , we have this 1.5 divided by two
05:27	and a quarter . First off , we're gonna turn
05:29	these into improper fractions . Okay , so if you're
05:33	not sure improper fractions , there will be a link
05:36	to a playlist in the description in this video .
05:38	Have a look at that . Okay , It's about
05:41	the third video along . Um So this is going
05:45	to become one , times two is equal to two
05:48	plus one is equal two , We're going to multiply
05:53	this by now . This is two times four which
05:57	is eight plus one , which is nine . So
06:01	this becomes 9/4 . We're going to use the reciprocal
06:03	, that 4/9 . What do we get when we
06:07	do that ? three , Uh , two times 9
06:12	is 18 . You can see here , Okay ,
06:15	we can simplify this . Six goes into both of
06:17	these . Six goes in two times six goes in
06:20	three times . This can't be simplified anymore . So
06:23	we have our answer there anyway . That's how you
06:26	go about dividing fractions . Hopefully you enjoyed that video
06:29	and it gave you some understanding why we actually flip
06:31	that number . I've been guilty of it myself in
06:33	the past as a math teachers said flip it and
06:35	multiply and not really got into why it occurs .
06:37	And I think it's an important thing why it occurs
06:40	. Anyway . We'll see you next time you need
06:43	any more help on fractions . There's an entire playlist
06:45	in the description below , as I've already said .
06:48	So use that if you have to . Okay ,
06:50	see you next time . Bye .

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Dividing Fractions is a free educational video by tecmath.

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