Math Antics - Converting Base-10 Fractions - By mathantics
Transcript
00:03 | Uh huh . Now that we know the basics of | |
00:07 | how decimal numbers work , Let's see how we can | |
00:09 | write some special fractions using decimal numbers . I'm going | |
00:13 | to call these fractions based 10 fractions because they're bottom | |
00:16 | numbers are all powers of 10 . Like 10 100 | |
00:19 | or 1000 . Let's start with this fraction 1/10 . | |
00:23 | You should recognize that it's one of our building blocks | |
00:26 | . And this should be easy to write down as | |
00:27 | a decimal number because we have a number of place | |
00:30 | just for counting 10th . So all we have to | |
00:33 | do is put one in the 10th place like this | |
00:36 | 0.1 . Now when you write decimal numbers it's important | |
00:40 | that you always include the ones place . But since | |
00:42 | we don't have anyone's we just put a zero in | |
00:45 | that spot . The zero makes the decimal point easier | |
00:47 | to see . All right , so that's 1/10 . | |
00:50 | But what if we have to over 10 instead ? | |
00:52 | Well all we have to do is change the digit | |
00:54 | in the 10th place to a two . So to | |
00:57 | over 10 equals 0.2 . In fact we can keep | |
01:01 | counting 10th like this . 3/10 456789 and finally 20th | |
01:07 | . But look what happened when we got to 20th | |
01:10 | now we don't have a digit for 10 . So | |
01:11 | we had to use the next number place over the | |
01:13 | ones place . But that makes sense because if you | |
01:16 | have the fraction 10/10 that makes a whole and the | |
01:19 | value is just one . Of course we don't really | |
01:21 | need the zero in the 10th place to write one | |
01:24 | but as long as the decimal points there at least | |
01:26 | we won't confuse it with tin . Alright 10th are | |
01:29 | pretty easy . But what about hundreds ? Let's start | |
01:31 | with the hundreds . Building block one over 100 . | |
01:34 | To write that as a decimal , we simply put | |
01:36 | a one in the hundreds place . We also need | |
01:39 | to put a zero in the 10th place to act | |
01:41 | as a placeholder and show that we have no tents | |
01:43 | and we still need to put a zero in the | |
01:45 | ones place as usual . Next let's try to hundreds | |
01:49 | for that . We simply put it to in the | |
01:50 | hundreds place . Let's keep on counting with hundreds , | |
01:53 | just like we did for 10th 304 56789 and 10 | |
01:59 | hundreds . Ah but look what happened when we got | |
02:02 | to 10 hundreds , just like before we have to | |
02:04 | use the next number place to the left , the | |
02:06 | 10th place . This happens because any time you have | |
02:09 | 10 of a building block , they combined to form | |
02:12 | one of the next biggest building block . For example | |
02:16 | , 1000s is a 10th . 10/10 is a one | |
02:20 | , 10 ones is a 10 and 10 tens is | |
02:23 | 100 . Now , the next fraction after 10 over | |
02:26 | 100 is 11 over 100 . Now , if you | |
02:28 | think about it , you'll see that 11 hundreds is | |
02:30 | really just a combination of 10 hundreds and 100 . | |
02:34 | Knowing that will help us write it as a decimal | |
02:36 | because a group of 10/100 is equal to 1/10 . | |
02:39 | We put a one in the 10th place and we | |
02:41 | still have that 1/100 leftover . So we put a | |
02:44 | one in the hundreds place , they're 11 over 100 | |
02:48 | is just 0.11 as a decimal . Fortunately you don't | |
02:52 | have to break up the fraction into 10th and 100th | |
02:54 | each time anytime you have a two digit number over | |
02:57 | 100 all you have to do is put those digits | |
02:59 | into the 10th and 100th . Place of your decimal | |
03:01 | number . Let's look at a few more examples to | |
03:04 | help you see the pattern . 24 over 100 would | |
03:07 | be 0.24 32 over 100 would be 0.3 to 78 | |
03:12 | . Over 100 would be 0.78 and 99 over 100 | |
03:16 | would be 0.99 Now what do you think will happen | |
03:19 | if we convert the fraction 100 over 100 into a | |
03:22 | decimal ? Right 100 has three digits so we need | |
03:25 | to use another number . Place Now . The next | |
03:27 | one over is the ones place . And that makes | |
03:29 | sense because 100 over 100 is a whole and its | |
03:32 | value is just one . Now that we know how | |
03:35 | to convert hundreds into decimals . Let's try converting thousands | |
03:38 | . That's fractions that have 1000 as the bottom number | |
03:41 | . Let's start with one over 1000 . Now this | |
03:44 | should be easy . All we have to do is | |
03:45 | put a one in the thousands place . Notice that | |
03:48 | this time we need zeros in both the 10th and | |
03:50 | 100th place to act as placeholders . Next , Let's | |
03:53 | strike in burning 10 over 1000 . Remember that 10,000 | |
03:57 | is the same as 100 . So put a one | |
03:59 | in the hundreds place and we'll put a zero in | |
04:02 | the thousands place . We don't really need the zero | |
04:04 | at the end , but it helps us see that | |
04:06 | this was 10 thousands . All right . What if | |
04:09 | we have 100 over 1000 ? That's a three digit | |
04:11 | number on top . So , we're going to need | |
04:13 | to use three number places , the thousands place the | |
04:15 | hundreds place on the 10th place . So , as | |
04:19 | you can see , 100 over 1000 is just the | |
04:21 | same as 1/10 . Let's see a few more examples | |
04:24 | , 58 over 1000 is 0.58 73 Over 1000 is | |
04:29 | 0.73 365 . Over 1000 is 0.365 and 999 over | |
04:37 | 1000 is 0.999 . And finally , what do you | |
04:41 | think we could get if we converted 1000 over 1000 | |
04:44 | ? Right ? Again , 1000 over 1000 is just | |
04:46 | a whole . So its value would be one . | |
04:48 | Okay , so we've learned how to convert based in | |
04:51 | fractions into decimals . But we can go the other | |
04:53 | way to we can start with the decimal and convert | |
04:56 | it into a fraction . Let's say we want to | |
04:58 | convert a decimal number into a fraction . All we | |
05:01 | have to do is take the decimal digits and make | |
05:03 | them the top number of a based infraction . The | |
05:06 | bottom number will be determined by the smallest number place | |
05:08 | used in our decimal for example , to convert 0.8 | |
05:12 | into a fraction , we put an eight on the | |
05:14 | top and a 10 on the bottom because the smallest | |
05:16 | number place in our decimal was the 10th place . | |
05:19 | And to convert 0.29 into a fraction we put a | |
05:22 | 29 on top and we put 100 on the bottom | |
05:25 | because the smallest number place in our decimal was 1/100 | |
05:28 | place . And finally to convert 0.568 into a fraction | |
05:32 | we put 568 on top and 1000 on the bottom | |
05:36 | because the smallest number place on our decimal was the | |
05:38 | thousands of place . Okay , so far all of | |
05:41 | the fractions that we've converted to decimal numbers and vice | |
05:44 | versa have bottom numbers like 10 , 100 or 1000 | |
05:48 | . Those fractions are easy to convert because our number | |
05:50 | system is based on powers of 10 . We have | |
05:53 | number of places specifically for counting those . But what | |
05:56 | if we want to take fractions with different bottom numbers | |
05:58 | like one half 3/4 or eight 25th and write those | |
06:02 | as decimal numbers . We don't have special number of | |
06:04 | places for halves , fourths or 25th . So what | |
06:07 | are we going to do ? Well you're gonna have | |
06:09 | to watch the next section to find out . But | |
06:11 | first let's take a minute and review all this . | |
06:14 | If a fraction has a bottom number that is a | |
06:16 | power of 10 , then it's easy to convert it | |
06:19 | into a decimal number because there are a number of | |
06:20 | places just recounting based infractions To convert tents . All | |
06:25 | you have to do is put the top number in | |
06:27 | the 10s . pl to convert hundreds . You have | |
06:30 | to use both attempts and the hundreds of place together | |
06:33 | . To convert thousands , you have to use three | |
06:36 | number of places and so on . You can also | |
06:40 | convert from a decimal number two , a fraction . | |
06:42 | Just by making the decimal digits , the top number | |
06:44 | of the fraction , and by using a bottom number | |
06:46 | that's based on the smallest number . Place from our | |
06:48 | decimal . You sure to do the exercises So you | |
06:51 | get really good at converting based infractions . Learn more | |
06:56 | at math antics dot com . |
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