BÀI 18 : DIVIDING DECIMALS.

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https://www.youtube.com/watch?v=brzZNmByyM4

Alright guys .

Now  let's look at dividing decimals .

Ooh  sounds scary but it's really not okay.

 So  we have two point four five divided by one point five .

And the first thing you want to do is take that second number or the divisor and make it an integer .

So  to do that we want to move the decimal.

 One  place to the right or multiply by ten it's another way of thinking about it.

But  ultimately we just want to make one point five into 15 .

Now  you'll notice we moved it one decimal place to get it into an integer .

And  we want to do the exact same thing with the first number.

So  we had two point four five .

We 're gonna make that twenty four point five because we move the decimal place one time in the first number .

We 're gonna do that now with this number .

Okay  so now the problem reads.

 Twenty  four point five divided by fifteen .

Okay so let's look at that and make that long division .

Okay  so we have twenty four point five.

 Now  this is the real tricky part you want to make sure that the first Number that we had before.

 Twenty four point five goes inside the house .

So it kind of looks like it's doing this criss-cross thing right .

Twenty  four point five goes in the house .

The division house as we say.

 And  fifteen goes out front .

The  other really important thing here is that you make sure to put the decimal place .

Right above where it is inside the house.

 So twenty four point five ,the decimal place is right after the four .

Make  sure the decimal point is right above that in your answer .

Now  we just divide left to right just the way that we do long division.

Okay  so we ask ourselves how many times does fifteen go into twenty four .

We  don't go over that now.

 But you'll recall there's a lot of different strategies how to figure that one out.

 15 goes into 24 one time.

 So  15 times one is 15 .

24 minus 15 is nine .

Okay  so that's our remainder there step.

 We 're gonna go ahead and bring that five straight down .

So  we're left with a remainder of 95.

 Okay  so how many times does 15 go into 95 .

We  ask ourselves again .

We 're not going to go over that particular concept now.

 But  you'll see that if you work it out ,you'll get 6.

 Ok so 15 times 6 is 90.

 95 minus 90 is 5.

 Ok so now what do we do.

 Well  we're gonna imagine that there's zeros going on for.

You  tell infinity after 24.5 .

Because remember there actually are zeros that go on to infinity after twenty four point five .

So  it's twenty four point five zero zero zero zero zero and so on.

So  we're gonna bring that zero down and we get 50 .

So  how many times is 15 go into 50.

Well  again if you work it out ,it's three so 15 times 3 is 45.

Now  watch out 50 minus 45 is five .

Now  check it out.

That 's exactly what we got on the step before .

Okay  now that's interesting .

What happens if we bring down that next zero.

Well  you'll see that you get this unending stream of 50 minus 45.

And you're gonna get three on to infinity .

So this is one of those cases where.

We  can stop.

We  can stop and say this decimal is going to keep repeating.

So  we have one point six three repeating.

As  our answer.

And  that's it .

That 's how you divide decimals.

You  just move the decimal in the divisor enough times to get an integer.

And  then move the decimal the same number of times in the dividend .

And  then do long division the way you normally do it.

And that my friends is how you divide decimals.

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