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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