Fractions of an unknown amount - fast math trick - By tecmath
Transcript
| 00:0-1 | Good day . Welcome to Tech Math channel . What | |
| 00:01 | we're going to be having a look at in this | |
| 00:02 | video , we're going to be looking how to work | |
| 00:04 | out fractions of an unknown number . It's a fairly | |
| 00:07 | simple sort of thing to do . Once you get | |
| 00:08 | the hang of it , a type of question , | |
| 00:10 | we're gonna be having a look at our ones like | |
| 00:12 | this . Okay , so , so you were asked | |
| 00:13 | three quarters Of what number is equal to 12 . | |
| 00:20 | Now when we're doing these , I think it's uh | |
| 00:22 | , look , I'm just going to go through a | |
| 00:24 | brief explanation of this fractions of a few . People | |
| 00:26 | tend to get thrown by these . And I think | |
| 00:28 | it's really , really important when you're looking at a | |
| 00:30 | fraction , you understand a few things . The first | |
| 00:32 | bit is , there's two parts to it . Obviously | |
| 00:34 | , uh , you know , top part in the | |
| 00:36 | bottom part , denominator numerator . If you get into | |
| 00:38 | that sort of jargon boots , what we're going to | |
| 00:41 | be realizing with these top and the bottom numbers . | |
| 00:43 | Is this the first off that part , when we're | |
| 00:47 | talking about three quarters what we're doing is we're talking | |
| 00:49 | about something a number being divided up four ways . | |
| 00:52 | Okay , so this is a dividing number here . | |
| 00:54 | And then we're talking , when we talk about is | |
| 00:56 | top number , is how many lots of this we're | |
| 00:59 | getting . So okay , this is like a timeline | |
| 01:01 | number . So we can so we're getting three quarters | |
| 01:03 | of the cake . We're talking about how we'd cut | |
| 01:05 | it up , Divide It four ways . And then | |
| 01:08 | we're talking about three groups of this . So where's | |
| 01:11 | the dividing ? And then we're times in . Okay | |
| 01:14 | . So if you can understand that , that's pretty | |
| 01:17 | a pretty good thing to get . So we're gonna | |
| 01:19 | actually trying to get this number , basically trying to | |
| 01:22 | get this part by itself . So we're trying to | |
| 01:24 | get this number over here . So to do that | |
| 01:26 | , we do the opposite of what these numbers are | |
| 01:29 | doing at the moment . So this is a timely | |
| 01:31 | number . It's going to become a dividing number at | |
| 01:34 | the moment . This is the dividing number . It's | |
| 01:36 | going to become a times in number . Okay ? | |
| 01:38 | So if you can remember that and take that in | |
| 01:41 | , you'll be pretty right . So When we do | |
| 01:44 | this , it's quite simple to do . Now we | |
| 01:46 | go 12 divided by three , which is four times | |
| 01:54 | four , It's 16 . All right . Through 16 | |
| 01:58 | . Okay , so let's have a look at another | |
| 02:00 | one of these . So hopefully you understood that . | |
| 02:02 | That's okay , if you didn't we'll go through another | |
| 02:05 | one . What about me too ? 2/5 of an | |
| 02:10 | unknown number Is equal to 18 . Okay , so | |
| 02:15 | , again , I think you should be able to | |
| 02:17 | look at the straight lines . Okay , this is | |
| 02:18 | r times the number and this is our dividing number | |
| 02:20 | over this side . So we're gonna be doing the | |
| 02:22 | opposite to 18 with these we're gonna be dividing by | |
| 02:25 | two and times it by five 18 divided by two | |
| 02:30 | is nine times 595 R 45 2/5 of 45 is | |
| 02:38 | 18 correct answer to . All right . Let's have | |
| 02:41 | a look at one more . These are really simple | |
| 02:43 | . Right ? Okay . Let's have a look at | |
| 02:45 | it . Ah say we had 5/8 of Mr unknown | |
| 02:51 | number here and as equal to 35 . All right | |
| 02:56 | again at the moment be thinking this is our Dividing | |
| 02:59 | number . This is r times the number . So | |
| 03:01 | we're going to be doing the opposite . We're going | |
| 03:04 | to go 35 divided by five . And we're gonna | |
| 03:09 | be times your answer by eight . So 35 divided | |
| 03:12 | by five which is seven times eight is 56 . | |
| 03:16 | And funnily enough you can do this in the opposite | |
| 03:18 | or eco 35 times eight and then divide your answer | |
| 03:23 | by five when you get the same answer . I | |
| 03:25 | just think it's often a lot easier to to deal | |
| 03:27 | with smaller numbers . So we're dividing and that sort | |
| 03:29 | of deal . Okay , So hopefully that was an | |
| 03:33 | explanation you understand on how to do these sorts of | |
| 03:35 | questions . And anyway , we'll see you next time | |
| 03:38 | . Okay , bye . |
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