Math Antics - What Are Percentages? - Free Educational videos for Students in K-12 | Lumos Learning

Math Antics - What Are Percentages? - Free Educational videos for Students in k-12


Math Antics - What Are Percentages? - By mathantics



Transcript
00:03 Uh huh . Hi . Welcome to Math Antics .
00:08 Now that you know all about fractions from watching all
00:10 of our fractions videos , it's time to learn about
00:13 something called percentages . Percentages are super important . Have
00:17 you ever been in a math class and heard another
00:19 student as a teacher ? Um Excuse me , A
00:22 teacher . When are we ever gonna use this stuff
00:26 ? You know like in real life ? Well ,
00:31 when it comes to percentages , the answer is 100
00:34 of the time . All right . Maybe not 100
00:37 of the time , but a lot percentages are used
00:41 every day to calculate things like , well , how
00:43 much sales tax you pay when you buy something ,
00:45 how much something costs when it's on sale . How
00:48 much fibers in your granola bar or how much money
00:51 you can make if you invested in the stock market
00:53 . That's all real life stuff . For sure .
00:55 So you can see that it's really important to understand
00:57 percentages and how we use them in math . All
01:00 right , then . Are you ready to learn the
01:02 key to understanding percentages or percent says they're called for
01:05 short drumroll , please ? A percent is a fraction
01:09 What ? That's right . A is a fraction .
01:13 And since you already know all about fractions , learning
01:16 about percent is going to be easy . But a
01:18 percent isn't just any old fraction of a percent is
01:21 a special fraction that always has 100 as the bottom
01:25 number . If it's a percent , the no matter
01:27 what the top number is , the bottom number will
01:30 be 100 . In fact , because the bottom number
01:33 of a percent is always 100 . We don't even
01:35 write it instead . We use this handy little symbol
01:38 called a percent sign . Whenever you see this symbol
01:41 after a number , it means the number is a
01:43 percent . It's really a fraction with 100 on the
01:46 bottom . But it's just being written in this more
01:48 compact form like this number 15 here it's got the
01:52 percent sign after it . So we read it as
01:54 15% . And because the percent is really a fraction
01:58 that always has 100 as the bottom number . We
02:00 know that it means the same thing as 15 over
02:03 100% . Make even more sense if you know what
02:06 the word percent means . The prefix of the word
02:09 per means for each or for every you know like
02:13 if someone said only one cookie per person and the
02:16 root word sent is Latin for 100 . That's why
02:19 there's 100 cents on the dollar . So percent literally
02:23 means per 100 And that's why they're shortcuts for writing
02:27 fractions that have 100 as the bottom number . All
02:31 right then . So whenever you see a percent like
02:33 this , you know it can be replaced with or
02:35 converted to a fraction . Let's look at a few
02:38 examples . So you see the pattern . three means
02:42 3 over 100 . 10 means 10 over 125 means
02:47 25 over 175 means 75 over 100 . These are
02:53 percents . And these are the fractions that they stand
02:56 for . There's a few other interesting percent that we
02:58 should take a look at like this 1 0% .
03:02 Can you have 0% ? Yes , 0% . Would
03:06 just mean zero over 100 . It's what we like
03:09 to call a zero fraction because its value is just
03:11 zero . Remember ? It's okay to have zero on
03:14 the top of a fraction , but not the bottom
03:16 . All right then . What about 100% ? Well
03:20 , 100 just means 100 over 100 . That's what
03:23 we like to call a whole fraction . The top
03:25 number is the same as the bottom . So its
03:28 value is just one hole or one . Okay ,
03:31 then 0% is just zero and 100% is just one
03:35 . But what about numbers bigger than 100 ? Can
03:37 you have 100 and 26% yep . It works exactly
03:41 the same way . 100 and 26% Just means 126
03:45 over 100 . And you know , from the fractions
03:48 videos , That's what we call an improper fraction .
03:51 The top number is bigger than the bottom number .
03:53 So the fractions value will be greater than one .
03:56 All right , team . I want you to go
03:58 out there and give me 110 effort in today's game
04:02 . But coach , it would be improper for us
04:04 to give 110 effort in today's game . Okay ,
04:08 so now , you know the key to percentages that
04:11 they're just special fractions that always have 100 as the
04:14 bottom number . But there's one more thing that I
04:16 need to tell you about in this video and that's
04:18 decimals . Do you remember in the video about fractions
04:22 and decimals that you can convert any fraction into its
04:24 decimal value ? Sometimes it was kind of tricky converting
04:28 to a decimal if we had to divide the top
04:30 number by the bottom number . But other times like
04:33 when we had based 10 fractions , it was easy
04:35 because decimal number of places are made for counting based
04:38 infractions like 10th , hundreds and thousands . Well guess
04:42 what percents are based infractions there ? Hundreds because they're
04:46 bottom number is always 100 . That means it's really
04:50 easy to rewrite a percentage as a decimal number .
04:52 You can do it the same way as we did
04:54 in the base 10 fractions video for example , we
04:57 know that 15 is just 15 over 100 . Right
05:01 ? That's it's fraction form But it also has a
05:03 decimal form . 0.15 . Because this is the hundreds
05:07 place and 0.15 means 1500s . So we can rewrite
05:14 15 as a fraction 15/00 or as a decimal 0.15
05:20 . And now that you know why we can easily
05:22 convert a percentage to a decimal . Let me show
05:25 you a really simple trick for doing it . First
05:28 you start with the number in form like this .
05:31 35% . Next you imagine where the decimal point should
05:35 be in the number 35 . It's not shown .
05:38 But if it was it would be right here next
05:40 to the ones place now . Remember 35 and 35.0
05:44 are the same value . Now that you know where
05:47 the decimal point is . Just move it to number
05:49 of places to the left away from the percent symbol
05:52 and draw it in right there . Last of all
05:55 , once you've moved the decimal point you erase the
05:58 percent sign because you don't have a percent anymore .
06:01 Moving the decimal .2 places to the left , converted
06:04 it into the decimal value of that% . Let's try
06:08 converting a few more percents into their decimal values .
06:11 So you can get the hang of it For 62%
06:14 . We move the decimal .2 places to the left
06:17 and get 0.62 . Remember we can put an extra
06:20 zero in front of the decimal point to be a
06:22 placeholder . And to make the decimal point easier to
06:25 notice for 75 we move the decimal point and get
06:29 0.75 for 99% . We move the decimal point to
06:33 get 0.99 . Pretty cool . Huh ? Okay .
06:37 But what about 4% ? You might wonder how we
06:40 can move the decimal point to places over when our
06:43 number only has one digit . But all we need
06:45 to do is use zero as a placeholder in the
06:48 number of place that's missing . Then when we move
06:51 the decimal point to places over , we end up
06:53 with a decimal value of 0.04 . Now that makes
06:57 sense because four is in the hundreds place and four
07:01 is for over a 100 And in the same way
07:04 one would just be 0.01 . Again we need that
07:08 extra zero placeholder . Here's a few more interesting examples
07:12 . zero would just be 0.00 . And if we
07:17 have 100 and we move the decimal .2 places to
07:20 the left , we end up with 1.00 . But
07:24 1.00 is the same value as one . And that's
07:28 why 100 represents one whole . And if we have
07:31 142% , we move the decimal point to get 1.42
07:36 , That's a value greater than one . Which is
07:38 what we would expect . Because 142 is really an
07:42 improper fraction . 142 over 100 . Its value should
07:46 be greater than one . All right . So now
07:49 , you know that a percent is a special fraction
07:51 that always has 100 as the bottom number . And
07:54 you know that you can rewrite percents in either their
07:56 fraction form or their decimal form . 25 is 25
08:00 over 100 or 0.25 . But keep in mind that
08:05 you could go the other way too . If someone
08:07 gives you a fraction with 100 as the bottom number
08:10 , you can rewrite it in percent form . If
08:13 you get 12 over 100 you can say that's 12%
08:16 . And if you get 80 over 100 you can
08:18 say that's 80% . Or if you get the decimal
08:21 0.10 you can say that's 10% . And if you
08:25 get the decimal 0.38 you can say that's 38% .
08:29 So that's the key to percentage . Is there another
08:32 way to write fractions and decimals ? But there's a
08:34 lot more to learn about how they're used in math
08:36 and we'll learn more about that in the next few
08:38 videos . But for now you should be sure that
08:41 you really understand the basics of percentages by doing the
08:44 exercises for this section . Thanks for watching Math Antics
08:47 and I'll see you next time . Learn more at
08:51 Math Antics dot com .
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