Multiplying Decimals - By tecmath
Transcript
| 00:0-1 | Good day . Welcome to the Tech Math channel . | |
| 00:02 | What we're going to be having a look at this | |
| 00:03 | video is we're gonna be looking at multiplying decimals with | |
| 00:05 | one another . We're gonna start off with an easy | |
| 00:07 | example and get into a harder example . Okay , | |
| 00:10 | just to build you up to that and once you've | |
| 00:11 | got the idea with this , you'll be fine . | |
| 00:13 | Now multiplying decimals is much like multiplying any number . | |
| 00:17 | It's just a couple of tricks to remember with it | |
| 00:19 | . So I'll start off with the knees example . | |
| 00:21 | So I did 1.5 times 2.3 . Now the way | |
| 00:28 | we go at multiplying this is much the same as | |
| 00:31 | any other . If we decided to 15 times 23 | |
| 00:34 | this just a couple of tricks we're gonna end up | |
| 00:36 | with the same numbers were just getting up with a | |
| 00:38 | decimal place being in a different spot and I'm going | |
| 00:41 | to show you how it worked in it . So | |
| 00:43 | I'm gonna write this first out , Just like a | |
| 00:46 | standard multiplication . So 15 times 23 units lineup at | |
| 00:51 | hands line up . Everything's good . I'm not gonna | |
| 00:53 | do any special ways of multiplication is I'm gonna do | |
| 00:55 | that . Pretty stock standard way . Okay , so | |
| 00:58 | we go five times three is 15 carry the one | |
| 01:02 | the one times three is three plus one is cool | |
| 01:09 | . Okay . We put a zero down here two | |
| 01:13 | times 5 is 10 . We carry the 11 times | |
| 01:18 | two is two plus one is three . And then | |
| 01:21 | what we're doing is we add these numbers together so | |
| 01:24 | we get a five four and a threat . Okay | |
| 01:30 | so 345 but that's not our answer . It would | |
| 01:33 | be it was 15 times 23 . That would be | |
| 01:35 | our answer . But we're going to be slightly different | |
| 01:38 | here . And the way that we deal with these | |
| 01:40 | decimal places as this . You look at both of | |
| 01:42 | your numbers here , say that first number you count | |
| 01:45 | the number of decimals to the right here . So | |
| 01:47 | behind the distant place . The part number parts . | |
| 01:50 | So there's from here there's one number behind the decimal | |
| 01:54 | place . Okay , I'll put it over here . | |
| 01:55 | There's one here . There's also one other behind the | |
| 01:59 | decimal place . So what we do is we add | |
| 02:02 | these numbers together . So one plus one equals two | |
| 02:05 | and two numbers . That means is the numbers that | |
| 02:07 | we should have behind the decimal place . So there | |
| 02:09 | were 3 45 . 2 of these numbers should be | |
| 02:11 | behind the decimal place . So one to our answer | |
| 02:16 | 3.45 . And that's how you work out where the | |
| 02:20 | decimal place goes . That's not too bad . Right | |
| 02:22 | . You're just going to work out again the number | |
| 02:25 | of decimal places here , the number of decimal places | |
| 02:28 | here , add them together and there we go . | |
| 02:32 | That's how many we have in our answer . So | |
| 02:34 | I'll give you another example here . Okay , the | |
| 02:40 | example we'll do now , it'll be a bit of | |
| 02:42 | a harder one . We will do , What about | |
| 02:45 | we do 20 1.7 and I'm going to times is | |
| 02:50 | by 0.6 one . Okay , So again , I'm | |
| 02:58 | gonna do this a very standard way . If you | |
| 03:00 | wanna really want to go faster , I do modification | |
| 03:02 | . I have other videos on this , but I'm | |
| 03:03 | gonna do this is fairly standard because I think people | |
| 03:05 | who are doing this , I don't want to learn | |
| 03:07 | something extra on top of it at the same time | |
| 03:08 | just to confuse them . So again I'll write things | |
| 03:11 | out so they line , I'm gonna treat this again | |
| 03:13 | sorry , like 217 Times 61 and then I'm going | |
| 03:17 | to deal with the decimal places . So All right | |
| 03:20 | , 217 . We're going to talk about this by | |
| 03:24 | 61 . So one time 77 we have one times | |
| 03:31 | one is one and one times two it's too 00 | |
| 03:36 | down there . Seven sixes are 42 carry the full | |
| 03:41 | 1 , 6 or six plus 4 . 10 carry | |
| 03:44 | the one 26 is 12 plus one is 13 . | |
| 03:50 | And now we're going to add our answer here . | |
| 03:51 | So we have seven three two plus zero is too | |
| 03:57 | 31 So how many decimal , why is this do | |
| 04:00 | we have ? Let's have a look here . We | |
| 04:02 | have one number behind the decimal place . Here . | |
| 04:06 | We have two numbers behind the decimal place . So | |
| 04:08 | one plus 2 equals three . So we have three | |
| 04:13 | numbers behind the desk . Always here . 123 Their | |
| 04:16 | answer Is 13.237 . Okay . And with this you | |
| 04:23 | can actually look at them and sort of say that | |
| 04:25 | makes it a bit of a sense because we're that | |
| 04:27 | makes sense . We don't we're a little bit over | |
| 04:28 | half of 21 so it's gonna be 13.2 . So | |
| 04:32 | it's not gonna be 1.3 because that's that would be | |
| 04:34 | too small and it's not gonna be 132 because that | |
| 04:37 | would be way too . Okay , this is just | |
| 04:39 | under just a little bit over half of 21 . | |
| 04:42 | Okay . So hopefully there was some help . The | |
| 04:44 | next we know what we're gonna be having a look | |
| 04:45 | at is how to divide decimals . It's a fairly | |
| 04:48 | similar sort of technique . I hope to see you | |
| 04:50 | then . Bye . |
Summarizer
DESCRIPTION:
OVERVIEW:
Multiplying Decimals is a free educational video by tecmath.
This page not only allows students and teachers view Multiplying Decimals videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.
GRADES:
STANDARDS:
