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### Course: 4th grade > Unit 10

Lesson 8: Common fractions and decimals# Common fractions and decimals

Explores the concept of converting common fractions (1/5, 1/4, 1/2) into decimals. Learn the importance of understanding these conversions for real-life applications and for working with multiples of these fractions.

## Want to join the conversation?

- how do you convert a percentage into a decimal?(70 votes)
- Move the imaginary decimal point two spaces to the left.

100% -> 1.00

50% -> 0.50

1% -> 0.01

You could also divide a percentage by 100 to get the decimal.

100%/100 is 1.00

50%/100 is 0.50

1%/100 is 0.01(132 votes)

- I tipped in 1/4 = 25/100 but it’s says it’s wrong why is that(21 votes)
- that is true but they are asking you to rewrite it as a decimal. 1/4 = .25(36 votes)

- I don't get how a fraction can be converted into a decimal.(15 votes)
- The simplest method to transform a fraction number to a decimal value is to simply divide the numerator by the denominator to get the decimal value. The numerator is the top number and the denominator is the bottom.(21 votes)

- can you times a decimal(14 votes)
- Yes. If you want to multiply a decimal, you have to just multiply the numbers, and put the decimal point in after. For example, 4 times 0.2 is 0.8.(16 votes)

- I can understand converting fractions to decimals but not decimals to fractions :((8 votes)
- Converting decimals to fractions is actually easier. It's all in how you SAY the decimal. For example:

0.2 is pronounced two tenths and then is written 2/10

0.35 is pronounced thirty five hundredths an then is written 35/100

Get the idea?(13 votes)

- The cursor in this video is too big for learners to see what you are writing. Maybe make it smaller?(9 votes)
- how do you subtract a decimal with a fraction?(4 votes)
- Convert either one to another format.

For example 12.3 - 45 / 6

Let's convert 45 / 6 to a decimal

12.3 - 7.5

= 4.8

Let's convert 12.3 to a fraction

123 / 10 - 45 / 6

= (123 * 6 - 45 * 10) / (10 * 6)

= 288 / 60

= 24 / 5(7 votes)

- I don't understand the 0.75 Question(4 votes)
- Another way of converting 0.75 to a fraction is to start by writing it as 75/100. Then you notice that both the numerator and denominator are divisible by 25, so you end up with 3/4.(5 votes)

- is there any way to practice problems that come up how he understood what if 4 doesn't go into 10 but then was like 4 does go into 100 . because i wouldnt have been able to realize that 4 goes into 100 so easy without figuring it out by actually trying to see if it does(5 votes)
- So what you do is 10/4 = 2.5 right but if you do 100/4 it equals 25 so just take away the decimal point(3 votes)

- David because he is funny and he says David out.(5 votes)

## Video transcript

- [Instructor] What we're
going to do in this video is give ourselves practice representing fractions that
you're gonna see a lot in life in different ways. So the first fraction we're
going to explore is 1/5 then we're going to explore 1/4 then we are going to explore 1/2. So let's start with 1/5. So I encourage you to
pause the video and say and think about how would you
represent 1/5 as a decimal. Well, there's a bunch of ways
that you could think about it. You could divide five into one. You could say that this is
equal to one divided by five and if you did that, you actually
would get the right answer but there's a simpler way
of thinking about this even in your head. You could say, well, let me
see if I can represent this as a certain number of tenths 'cause if you know how many tenths, we know how to represent
that as a decimal. Well, to go from fifths to tenths, you have to multiply
the denominator by two. So let's multiply the
numerator by two as well. So 1/5, one times two is
the same thing as 2/10 and we know how to represent
that in decimal notation. That's going to be 0.2. This is the tenths place. So we have exactly 2/10. Now, let's do 1/4. Same idea. How could I represent this as a decimal? Well, at first, you might say, well, can I represent this
as a certain number of tenths and you could do it this way but 10 isn't a multiple of four so let's see if we can do
it in terms of hundredths 'cause 100 is a multiple of four. Well, to go from four to 100,
you have to multiply by 25. So let's multiply the numerator by 25 to get an equivalent fraction. So one times 25 is 25. So 1/4 is equal to 25/100 and we can represent
that in decimal notation as 25/100 which we could also consider 2/10 and 5/100. Now, let's do 1/2. Same exact idea. Well, 10 is a multiple of two so we can think about
this in terms of tenths. So to go from two to
10, we multiply by five. So let's multiply the
numerator by five as well. So 1/2 is equal to 5/10 which if you wanna represent
as a decimal is 0.5, 5/10. Now, why is this useful? Well, one, you're gonna
see these fractions show up a lot in life and
you're gonna go both ways. If you see 2/10 or 20/100 to be able to immediately
recognize, hey, that's 1/5 or 25/100, hey, that's
1/4 or 1/4, that's 25/100. 1/2 is 0.5 or 0.5 is 1/2 and it's not just useful
for these three fractions. It's useful for things that are multiple of these three fractions. For example, if someone said, quick, what is 3/5 represented as a decimal? Well, in your brain, you could say, well, 3/5, that's just
going to be three times 1/5 and I know that 1/5 is 2/10 so that's gonna be three times 2/10 which is, well, three times two is six so three times 2/10 is 6/10. So really quick, you're able to say, hey, that's 3/5 is 6/10 and you could have gone
the other way around. You could have said 6/10
is equal to two times, is equal to three times 2/10 and 2/10 is 1/5. So this is gonna be
equal to three times 1/5 and once again, these are just things that you'll get comfortable with the more that you get practice. Let's do another one. Let's say you wanted to represent, let's say you wanted to represent, let me do it another way. 0.75 as a fraction. Pause the video, try to do it yourself. Well, you might immediately
recognize that 75 is three times 25 so 75/100 is equal to three times 25/100 and 25/100 we already know is 1/4 so this is equal to three times 1/4 which is equal to 3/4 and over time, you won't have to do all
of this in your head. You'll just recognize 75/100, that's 3/4 because 25/100 is 1/4 and now let's do, let's say we have, let's say we have 2.5 and we wanna represent that as a fraction. Well, there's a bunch of
ways that you could do this. You could say, well,
this is five times 0.5 and that's going to be five times 1/2. Well, that's going to be 5/2. It's an improper fraction
but it's a fraction. And so once again, the whole point here and you might already be familiar with the different ways of converting between fractions and decimals but if you recognize 1/5, 1/4, 1/2, it's going to be a lot easier. Notice if you did it the other way around it'd be a little bit more work. If I said, let me
convert 3/5 to a decimal, well, then you would have
to divide five into three. Five into three and you'd say, okay, five goes into three zero times
so let's put a decimal here. Now, let's go to 30. Five goes into 30 six times. Six times five is 30. You subtract and then
you get no remainder. So this wasn't a ton of work but this one, the reason why I like this one, not only is it faster but it
gives you a better intuition for what actually is going on.