Percentage increase and decrease - By tecmath
Transcript
| 00:0-1 | Good day and welcome to the Tech Mouth channel . | |
| 00:02 | What we're gonna be having a look at this video | |
| 00:03 | is how to increase or decrease in number 5% . | |
| 00:06 | So , we're gonna look at , uh , some | |
| 00:08 | nice straightforward ways of doing this and I'm gonna show | |
| 00:11 | a bit of a shortcut way . So we're gonna | |
| 00:13 | go through the way which you probably are gonna be | |
| 00:15 | learning when you learn how to do this . And | |
| 00:17 | it's a nice logical way to understand What's happening on | |
| 00:20 | the increasing number 5% . But I'm gonna show you | |
| 00:22 | a couple of shortcuts you can use to increase the | |
| 00:24 | number 5% or decrease the number 5% . So , | |
| 00:29 | I'll give you an example of type of question we | |
| 00:31 | get with this . So say I wanted to Uh | |
| 00:34 | huh at the number 50 and I want to increase | |
| 00:37 | it by 20 percent . Okay , So I want | |
| 00:43 | to increase 50 by 20% . 20 by the way | |
| 00:45 | , 20%, , you might remember . It's just a | |
| 00:49 | number out of 100 . So 20% literally means 20 | |
| 00:53 | Out of 100 . Okay , so if we could | |
| 00:58 | work out what 20% of 50 was . This is | |
| 01:01 | the first one . I'll show you how to do | |
| 01:02 | it , then I'll show you the other ways that | |
| 01:04 | might point for a third way . If you can | |
| 01:06 | work out what 20% of 50 was , you could | |
| 01:09 | add it to 50 . Okay ? So we got | |
| 01:10 | 20% is and then you add it to 50 and | |
| 01:13 | you find out what 50 plus 20% is okay ? | |
| 01:16 | Where you increase it by 20% . So let's work | |
| 01:19 | out 20% of 50 . So we use this fraction | |
| 01:22 | form of 20% to 20 over 100 . And we | |
| 01:25 | do this with times it by 50 50 over what | |
| 01:32 | ? Okay . And if you're not sure how to | |
| 01:33 | do this , I have some other videos that do | |
| 01:35 | look at this . Okay . So What we now | |
| 01:38 | can do is you might remember uh is you can | |
| 01:41 | start counseling our numbers . Okay ? You can start | |
| 01:43 | dividing the same number into the top and the bottom | |
| 01:45 | . So 10 goes into both this number here and | |
| 01:47 | this number here . So we can get rid of | |
| 01:49 | those zeros . Ted also goes into this number here | |
| 01:53 | and this number here so we can get rid of | |
| 01:55 | these heroes . And what we're left with is this | |
| 01:58 | two times five is ted one , tolls , 1 | |
| 02:02 | is one And this equals 10 . Okay . So | |
| 02:07 | what now I'm going to have is this I'm going | |
| 02:08 | to have 50 And I'm going to be adding this | |
| 02:12 | 20% of 52 . It's I'm increasing 20% of 50 | |
| 02:15 | was 10 . So 50 plus 10 equals 60 . | |
| 02:21 | Okay . That's a way that you can really , | |
| 02:23 | really easy work out uh you know how to increase | |
| 02:27 | , say 50 by 20% . Okay ? Or or | |
| 02:29 | whatever number by whatever percent work out what the percentage | |
| 02:32 | of it is and then added on . Or decrease | |
| 02:34 | it if you're trying to decrease by percentage . But | |
| 02:36 | I'll show you a little shortcut that you can use | |
| 02:38 | with this . And this is as follows . Okay | |
| 02:40 | , So You might want to keep that answer in | |
| 02:42 | your head is 60 . Okay ? Because we'll use | |
| 02:44 | that same sort of problem . And I'm gonna try | |
| 02:46 | and explain this now , where you might uh It's | |
| 02:51 | just a little conceptual thing here . A little idea | |
| 02:53 | that that might help you understand this . If you | |
| 02:56 | can understand that we're starting with this whole amount here | |
| 02:58 | . This 50 . Okay . This I'm gonna Just | |
| 03:01 | draw it as a circle here . It's it's almost | |
| 03:03 | like a one . Okay ? It's it's the whole | |
| 03:05 | thing , but it's worth 50 . Okay . And | |
| 03:08 | I'm trying to increase this By 20% of this amount | |
| 03:12 | . OK Which The other thing you might understand this | |
| 03:16 | ? This is not only 20 out of a 100 | |
| 03:19 | But you also might understand this if you work at | |
| 03:22 | what 20 divided by 100 years we'll give you point | |
| 03:25 | to . Okay . And another way you can work | |
| 03:28 | out you can convert from a percentage to a decimal | |
| 03:30 | . Really quick is just divide this number by 100 | |
| 03:32 | . Move the decimal place twice 12 and 8.2 . | |
| 03:35 | So we have a decimal form now of 20% . | |
| 03:39 | Okay so I want to increase it by 0.2 . | |
| 03:44 | Okay so really what I'm doing Because I'm actually trying | |
| 03:46 | to find out what 1.2 . Okay because I've got | |
| 03:50 | the one here and I'm adding .22 at 1.2 . | |
| 03:54 | Okay because at these together of 50 years . Okay | |
| 03:57 | , so 1.2 times 50 . Okay , do you | |
| 04:02 | see this ? Hopefully I'll go through a few examples | |
| 04:04 | in a little bit . Uh so 1.2 times 50 | |
| 04:07 | , this is very much the same as 12 times | |
| 04:10 | five . 12 times five it's 60 . Okay . | |
| 04:18 | All right , I'll give you an example of again | |
| 04:21 | how you might actually convert these sort of things . | |
| 04:22 | Okay ? So I think I may lose a few | |
| 04:25 | people that they know what's going on there . So | |
| 04:27 | I'll try to re explain this again . I'll try | |
| 04:29 | to give you a few examples of what you would | |
| 04:31 | get uh say with some questions . So we were | |
| 04:33 | trying to uh not even where I'm working out straight | |
| 04:37 | away , but where I'll just show you how the | |
| 04:39 | equation you would be doing to work it out To | |
| 04:42 | say we wanted to work out what uh we had | |
| 04:45 | 70 and I wanted to increase this by 30% . | |
| 04:51 | Or I had 90 and I wanted to decrease this | |
| 04:56 | by 45% . Or I had 100 and I wanted | |
| 05:03 | to increase this by say 12% . Okay , There's | |
| 05:10 | a couple of questions here . Now . The way | |
| 05:12 | that you would set this up is as follows , | |
| 05:14 | it's the same as getting 70 here and This is | |
| 05:19 | going to be a .3 . So this is the | |
| 05:20 | one part . But this is a this is a | |
| 05:22 | decimal .3 . So at this , because I'm adding | |
| 05:25 | it on to this one part here , I've got | |
| 05:27 | 1.3 times in these numbers that will give me more | |
| 05:30 | answer . Okay , So you might be able to | |
| 05:34 | work that is that would be 91 . Okay , | |
| 05:39 | Because 7 , 3 , plus 70 is 91 . | |
| 05:43 | What about we do ? So I wanted to take | |
| 05:46 | 45% off . You might see the trick with this | |
| 05:49 | one because this again as a decimal 10.45 but now | |
| 05:54 | I'm not adding it to this one part here , | |
| 05:56 | I'm taking it away . Okay , Because this one | |
| 05:58 | we had one and we're adding it to one point | |
| 06:01 | to 1.0.3 . This one we're taking it away . | |
| 06:03 | So what we're actually ending up with is one takeaway | |
| 06:08 | .45 is zero 55 Okay . And I'm going to | |
| 06:15 | be times in this bond authority . Okay . So | |
| 06:22 | what's the answer to that ? Well away that you | |
| 06:27 | might work this out is as follows when you could | |
| 06:29 | just times these guys straight out . But I would | |
| 06:31 | try to think of this maybe like this if you | |
| 06:32 | can imagine this our .5 years which is half of | |
| 06:36 | 90 , which is 45 . Okay . And then | |
| 06:39 | we've got another , we've got 2.05 which is going | |
| 06:42 | to be 1/10 of the half there . So this | |
| 06:44 | is 4.5 . We're gonna add these together , so | |
| 06:48 | answer equals 49 0.5 . Okay , what about we | |
| 06:56 | do one more ? We do this one here , | |
| 06:58 | so this one We divided by 100 . We end | |
| 07:01 | up with .1 to this , we're adding this one | |
| 07:05 | here , we're going to be Times you by 1.12 | |
| 07:10 | And we're times this by 100 . It's a nice | |
| 07:13 | easy one , isn't it ? Because all I'm really | |
| 07:15 | doing is moving the decimal place 12 times 12 So | |
| 07:18 | the answer is going to be 100 and 12 , | |
| 07:21 | so hopefully you understand how to do that . I | |
| 07:23 | think it's a lot faster than working at 12% . | |
| 07:25 | This one is actually fairly easy because you can work | |
| 07:27 | at , you know , 12% of 100 is 12 | |
| 07:30 | and then add it on straight away . So this | |
| 07:31 | one's a fairly quick one . But some of these | |
| 07:33 | ones are , it's a fair bit faster . I | |
| 07:35 | reckon to be able to just uh you know where | |
| 07:37 | you go 90 times 900.55 Okay . Um anyway , | |
| 07:42 | hopefully that was of some help to you . Any | |
| 07:44 | questions ? Any comments please place that my wife is | |
| 07:47 | happy to uh see how you guys are doing anyway | |
| 07:50 | , See you next time . Bye . |
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