Multiplication and Division - Free Educational videos for Students in K-12

Multiplication and Division - By tecmath

Transcript


00:0-1	Good day and welcome to take Math Channel . What
00:01	are we having a look at this video of this
00:04	video ? Anyway , as a response to a comment
00:06	I've had on one of my other videos where somebody
00:08	was actually asking , they had a test coming up
00:11	and there was they were struggling with this multiplication and
00:13	division to standard multiplication division . So I thought I'll
00:17	make a quick video which they can have a look
00:19	at just to give him a hand so this might
00:21	help a few other people as well . I'll put
00:23	it out there . Anyone . Um let's have a
00:26	bit of a look at this . So the way
00:27	I do this is I'll just give a couple of
00:29	examples . I work through them for first multiplication and
00:32	then for division . So let's have a look .
00:35	So first off say you got the question where you
00:37	were asked to multiply say something like 300 five times
00:47	17 . First off , we have to write this
00:50	a different way . Okay . And setting out of
00:53	this is really , really important when you're doing this
00:54	. So let's get into the setting out of there
00:56	. So when you do this You would write the
00:59	305 . We're gonna be times in this by As
01:04	I've given myself a space here with my time .
01:06	It's not gonna collide in my 17 here in the
01:08	17 should line up . So the tens part of
01:11	the 17 lines up with the 10th part here and
01:13	the seven and the units all line up together there
01:16	. Okay . So notice that the units lineup ,
01:18	The 10s line up the hung its lineup . So
01:21	we put this over a line here and we're gonna
01:23	work this out now before we go with this ,
01:26	I'll explain this just on this particular one . The
01:29	way that we work this out is as follows ,
01:30	we're gonna work this out in parts first off where
01:33	we stand and working out multiplication like this . We
01:35	work out we work out what ? Seven Times 305
01:40	years . Okay ? And then we work out also
01:44	What ? 10 times 305 years ? Okay ? And
01:49	we're gonna by doing that . So that's the first
01:51	part . We're gonna we're the second part and we're
01:52	gonna add in together . So seven times 305 and
01:55	10 times 305 . And then all together we're gonna
01:57	have 17 times 305 which will be our answer .
02:01	Okay ? So we're gonna add these at the end
02:04	. Okay what our answers are ? So first off
02:07	, let's work out this seven times 305 . So
02:11	we start on the units park and we're gonna basically
02:13	seven times 57 times Nothing in seven times 300 .
02:19	We're adding our answers together and I'll show you how
02:21	we do this . So seven times five is 35
02:24	. Now we put the five down And with it
02:28	because it's 35 Before the fire part of that down
02:31	to the three bar because it's a 10 spot ,
02:33	we're actually going to carry that across to the next
02:36	one . So we only actually put the units part
02:37	of our answer down . The rest we carry across
02:40	the next part of the answer . Okay , so
02:42	the three goes here , zero times 70 times seven
02:47	is zero . Let me add that number we carried
02:49	across . Yeah , so zero times seven is 0
02:53	Plus three is 3 . Okay , Let's go there
02:59	. six parts of this . Is that 300 times
03:02	seven ? So three times seven Is 21 . Now
03:06	I'm going to write the whole amount down here because
03:08	there's nothing else over here . So there's nothing to
03:10	carry too . So I'm putting the one down then
03:12	that too would carry across but I might as well
03:14	put it straight down here because it's just gonna get
03:16	added to nothing and will end up being there .
03:17	Can't have that makes sense . Okay . The next
03:20	part so that's seven times 305 . That's this one
03:23	here . The next one we're gonna do is 10
03:25	times 305 . Yeah . Anything now in this tens
03:29	part of what you do is you put zero down
03:31	because there's 10 is going to add a zero To
03:35	the standard multiplication . There was hundreds within add two
03:38	Zeros . OK so we then go I'm not usually
03:41	one times five because it's not one times five it's
03:45	actually 10 times 5 . 10 times five is 50
03:49	. So we've already taken care of that . 01
03:51	times five is 5 . 10 times five is 50
03:54	times um one zero And one times three which is
04:01	the same as actually 10 times 300 Which is 3000
04:05	, but once on three Is through because that's actually
04:08	in the 3000 position . Okay , So we've got
04:13	our two hearts that we got a seven times 305-10
04:17	times 305 . Now , like I said , to
04:20	get 17 times 205 we're gonna add our answers together
04:23	. So let's do this five plus nothing . We
04:26	start again on this right hand side , five times
04:28	0 is five , three Plus 5 is right ,
04:34	one plus zero is one and two plus three .
04:38	It's five and that is our answer . That's our
04:42	final answer there . Okay , So hopefully you're pretty
04:47	good with okay now look , don't get despondent if
04:51	you do a couple of these and you make a
04:52	few little errors , the biggest trick to try and
04:55	do with them is if you do a couple of
04:56	them and you get a you say you can write
04:58	them down , you might get a calculator and you
05:01	can then actually , you know , check your answers
05:03	on the calculator . But if you make a mistake
05:05	, just trying to find out where it is ,
05:07	it's okay to make mistakes . I make mistakes to
05:09	occasionally when I multiply . All right , the wrong
05:11	thing down , even then you probably know this occasionally
05:13	. I might say the wrong thing or I might
05:15	you know that that that happens , that's okay ,
05:17	It's okay , you can do that , okay ,
05:19	the process is really good and eventually get them more
05:22	and more correct . So let's go through one more
05:25	example of this . So we have um what about
05:35	we do say something like 1015 and then at times
05:40	that by 27 . So we write this out as
05:44	follows Actually that sometimes this by 271 . Let's make
05:49	it a bit more interesting . A bit of a
05:50	bigger sort of question . Okay , so Let's do
05:54	this right now . So we go 1015 , Write
05:59	it out that nice way . 1st 1015 And this
06:03	is going to be times by 271 . Notice again
06:07	, the units lineup , the tans lineup , the
06:09	hundreds lined up and so on so forth . So
06:13	this is actually going to be um done Over three
06:19	parts . Okay , four parts . Now we're actually
06:21	gonna have 1015 and I'm gonna times that by one
06:26	Only times 1015 by 70 70 part here . Also
06:32	in the times 1015 by 200 . And then I'm
06:37	gonna add all these together to get our answer .
06:40	Okay , so let's do that . This 1000 and
06:43	15 times one first . This is really easy .
06:45	Times in my one because 15 is five , 11
06:48	is 11 times zero is zero and one times one
06:51	is one . Look at that easy . Okay ,
06:54	one times 1015 is 1015 . That seems pretty correct
06:59	. Okay , the next time is why 70 ?
07:02	So we're gonna take care of that zero . We're
07:03	gonna put the zero . Okay , so we put
07:06	10 there because it's a 70 part , not seven
07:09	. We're on 7535 . So we put the five
07:13	down , we carry the three , 1 77 Plus
07:19	three is 10 ft the zero down to carry the
07:22	one . So zero times seven . Zero plus one
07:31	is what ? and one time 7 is seven .
07:38	Okay , so that's this part done Now . Let's
07:43	go to this final part which is 1015 times 200
07:46	. So because it's a hundreds now we have to
07:50	put down two zeros . That's what hundreds are two
07:53	zeros . So let's do this five times two is
07:57	10 . We're gonna put that down there . You
07:59	know , look I want to use a different color
08:01	here because otherwise I've already got some stuff there .
08:03	So five times two is 10 . I'm gonna carry
08:06	that with the one there . Um five times two
08:11	is 10 . 1 times two is two plus one
08:13	is three . Okay ? zero times 2 . zero
08:19	and two times 1 is two . Okay . You'll
08:23	see that even here I struggle because I was trying
08:25	to get everything squashed in and so it all stayed
08:27	in the line there . It's really , really important
08:29	to do that to keep things in a line .
08:31	Okay , So what are we gonna do with this
08:33	now ? I'm gonna have them five plus 050 is
08:36	five . We're starting from the right hand side for
08:38	the last five or six . 0.1 plus one plus
08:43	three . It's five 7-17 . And the two guys
08:50	there , so there is our answer . Okay ,
08:54	let's get this some division now and I'll show you
08:55	how to do this . A couple of questions of
08:58	division . All right . So say the question you
09:05	had was this ? So we wanted to do 3065
09:11	Divided by five . Now , this should go in
09:14	without a remainder . We'll have the next time when
09:15	we deal with the remainder . Okay , so the
09:18	way that we write this is a little bit different
09:20	. Okay , the way we do these division ones
09:22	is we write them as follows . We write 3,065
09:29	and we put one of these . It's not very
09:31	straight lines . Yeah , he has a terrible straight
09:34	line . one of these sort of shapes that's better
09:39	around it . Okay , so divided by five .
09:44	Okay , now the way that we do this is
09:46	as follows . These are really , really simple .
09:48	Actually . We start dividing from the left hand side
09:51	here . So 5123 and five into work and five
09:54	into this and five into this and any remain .
09:57	Is there anything like this ? We carry across as
09:59	we go and these help us get our answer .
10:01	So I'll show you how this works . So three
10:05	divided by five . Three divided by five . Well
10:09	look , that's it doesn't work because finds much bigger
10:12	than three . So why five does go into three
10:15	? It doesn't go with a nice hole number answer
10:17	. So because it doesn't go it took three is
10:20	too small . We put a zero there and we
10:23	get the three and we carried across . Okay ,
10:26	so anything that's left over , which is this three
10:29	here , we carry across the next part , evidence
10:32	and this becomes a 30 . So five into 30
10:36	. How many times he goes six times with no
10:39	reminders . We have nothing to carry across . five
10:44	into 6 . six , divided by five . Six
10:48	five , goes into 6 . 1 time . And
10:50	there's one left . I was this one . We
10:53	carry on to the next part of our answer .
10:54	And then we have this becomes a 15 5 15
10:59	. There's three times . So this is how you
11:03	do this division . Okay , that's our answer .
11:06	There's nothing more to divide . That's the finished answer
11:09	. So what about I'll give you one more of
11:11	these . Um We do the one where we are
11:15	doing say something like uh to what ? 20,780 nine
11:23	. And we're gonna divide nine into this . Okay
11:27	, so we write this the same sort of way
11:29	20,789 . And such a messy line and dies going
11:39	into this . Okay . The way we do it
11:43	again , we start from the left , so two
11:45	divided by nine and we can't do that because too
11:48	small than nine . So we carry this to across
11:50	put zero there , we carry the two across .
11:53	Really important to put that zero there . Um Doesn't
11:55	matter so much here , but occasionally a bit later
11:57	when you can't do it , it's important to put
11:58	the zero there . Okay . Because So you say
12:03	you had something like 208 and you didn't zero there
12:06	, you would end up with the answer of 28
12:07	and 200 days . The answer , so just just
12:10	be careful that are off the zero does actually matter
12:14	. Yeah , 1920 goes twice two times because 29
12:19	18 And there is two left over 1927 . Well
12:25	it goes exactly three times . Okay So no reminder
12:30	, there's no 1-8 19-8 . I won't say we
12:33	can't do that . There's nothing , there's no no
12:35	no no way that goes in . So we put
12:39	a zero there like I said it's really important to
12:41	do this . Okay so put the zero there and
12:43	we carry the aid across and no one I know
12:47	it well no one does , no one knows the
12:49	81 . So there's nine times and there is a
12:53	reminder that is left over . So what do we
12:56	do with this ? 8 ? Because the eighth sort
12:57	of left on its own here . Occasionally you might
13:00	write this has remained er eight or occasionally you can
13:05	put this as a fraction where you would call it
13:07	, say right Over nine , okay ? Because they
13:11	were divided by nine . Okay ? So maybe you're
13:14	going to leave it like this one . Okay ?
13:16	Uh you're just starting out okay . Hopefully that was
13:19	some help . Let us know how you go .
13:23	Yeah . Let us know how you going this test
13:24	if if you do any good with it , but
13:27	do study these again , right ? Some up on
13:30	a calculator and again , look at the reasons if
13:33	you don't get them right , don't give up straight
13:35	away . Look at the reasons why you don't you
13:36	will get better at Okay , that's what this study
13:39	is sometimes going over things a bunch of times as
13:42	frustrating as I can feel . Anyway . We'll see
13:46	you next time , thought .

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Multiplication and Division is a free educational video by tecmath.

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