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  • - [Instructor] Let's see if we can figure out

  • what two divided by 0.1 or one tenth is.

  • Pause this video and see if you can figure that out.

  • Alright, now let's work through it together

  • and there's a couple of ways that we can approach it.

  • One way is to think about everything in terms of tenths.

  • So two wholes is how many tenths?

  • Well a whole is equal to 10 tenths,

  • so two wholes is equal to 20 tenths.

  • So I could rewrite the two as 20 tenths.

  • And so that's gonna be 20 tenths divided by,

  • instead of writing it this way,

  • instead of just writing it as 0.1,

  • we know this is the same thing as one tenth.

  • So divided by one tenth.

  • And so if I have 20 of something

  • and if I divide it into groups of one of that something,

  • how many groups am I going to have?

  • Well I'm going to have 20 equal groups of one.

  • So 20 tenths divided by one tenth is equal to 20.

  • Another way that you could approach that is you could

  • rewrite the 0.1, the one tenth, as a fraction.

  • We could rewrite this as two divided by.

  • Divided by.

  • Instead of writing one tenth like this,

  • I could write it as a fraction.

  • Divided by one tenth.

  • Well, we know that dividing by a tenth is the same thing

  • as multiplying by 10.

  • So this is going to be equal to two times.

  • Two times 10.

  • And that gets us to the same place that we had before.

  • What is two times 10?

  • Well that is going to be equal to 20.

  • And that's good that we got to the same answer.

  • Otherwise, these would not be equivalent methods.

  • Let's do another example.

  • So let's say we wanted to figure out what six divided

  • by one tenth is.

  • Pause this video and see if you can figure that out.

  • Alright.

  • Well, you could do the same idea.

  • Six wholes is equal to how many tenths?

  • It's equal to 60 tenths.

  • So I'll rewrite this as 60 tenths divided by one tenth

  • is equal to how many is equal to what?

  • Well if I have 60 of something

  • and if I divide it into groups of one of that something,

  • I'm gonna have 60 equal groups of one.

  • So this is going to be equal to 60.

  • So you might see a pattern.

  • When we divided by a tenth, we ended up multiplying by 10.

  • When we divide by a tenth, we are multiplying by 10.

  • And you could do the same thing as we saw up here.

  • You could say six divided by one tenth is the same thing

  • as six divided by one tenth written as a fraction

  • which is going to be equal to six times.

  • You can say six times 10 or six times 10 over one.

  • Either way.

  • Six times 10 over one or which is the same thing as 10

  • which is once again going to be equal to 60.

  • So I think you see the general pattern.

  • Divide by a tenth same thing as multiplying by 10.

  • Now what about if we dealt with hundredths?

  • So let's say we wanna figure out what seven divided

  • by a hundredth is?

  • What would this be?

  • Pause the video and try to figure it out.

  • Alright, well we can do the same drill.

  • So seven wholes.

  • One whole is equal to a hundred hundredths

  • so seven wholes is equal to 700 hundredths.

  • So this is equal to.

  • I'll write it like this.

  • 700 hundredths divided by.

  • Divided by one hundredth.

  • One hundredth.

  • If I have 700 of something and if I'm dividing it into equal

  • groups of one of that something,

  • I'm gonna have 700 equal groups.

  • So this is going to be equal to 700.

  • So you divide by a hundredth

  • is the same thing as multiplying by a 100.

  • Now you could also rewrite this as a fraction if you like

  • so that some of the principles we saw up here still apply.

  • So we could rewrite this as seven divided by one hundredth.

  • And so this is going to be the same thing as seven times

  • 100 over one.

  • Or seven times 100.

  • Seven times 100 which once again, will get you to 700.

  • So I think you see a pattern.

  • Divide by a tenth, same thing as multiplying by 10.

  • Divide by a hundredth, same thing as multiplying by a 100.

- [Instructor] Let's see if we can figure out

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A2 初級

除以十分之一和百分之一時的模式 (Pattern when dividing by tenths and hundredths)

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    林宜悉 發佈於 2021 年 01 月 14 日
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