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## Regrouping decimals

Current time:0:00Total duration:6:55

# Decimal place value with regrouping

CCSS Math: 4.NF.C.6

## Video transcript

We're told that "Each square below
represents one whole." So this big square right over here
is a whole, and then this big square over here
is another whole. Then they ask us "Which of the following
does the shaded area represent? Select all that apply." So let's see--
the shaded area. We're shaded in blue. So let's see-- one way to think about it
is we have 1 whole over here. and then over here we've divided it
into tenths: there's 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 equal sections,
and we've shaded in one of them. So we've shaded 1 tenth.
So this would be 1 whole and 1 tenth. So we could say that this
is 1 and 1 tenth. So that's one way to think about it,
but what about these other ones? Well even this one has been
divided into tenths, and you can view 1 whole
as 10 tenths. You see that here, where we've divided it
into 10 equal sections. 10 tenths, and we've shaded all 10 tenths in.
So this whole you could view as 10 tenths:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10. And then we have an 11th tenth. So we have-- if you count these
blue rectangles, we have 11 tenths. So you could also write this as 11 tenths. Now 11 hundredths? No, I don't think--
we haven't even divided this into hundredths,
and 11 hundredths would be a little more than 1 tenth. And so
this is definitely way more than that. So I could check my answer (and
actually you don't see it but it's happening off-screen) but this is
what I would go with for that. Let's do a couple more of these. So it says "Which of the following
describes the location of the point on the number line?" Let's see. I have 1, and then between 1 and 2
I've divided it into 10 equal spaces. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. So each of these tick marks,
or hash marks, is going to be a tenth. So this is 1 and 0 tenths,
1 and 1 tenth, 1 and 2 tenths, 1 and 3 tenths, 1 and 4 tenths,
1 and 5 tenths, 1 and 6 tenths, 1 and 7 tenths,
1 and 8 tenths. So 1 and 8 tenths is the same thing
as 1.8. 1 and 8 tenths. So it's that. But what about
these other options? Well one way we could think about
this is-- let's just count the tenths. Each of these hash marks is a tenth. So 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. It makes sense. A whole is 10 tenths. Let's keep going, we were at 10 tenths.
11 tenths, 12 tenths, 13 tenths, 14 tenths, 15 tenths,
16 tenths, 17 tenths, 18 tenths. This one also applies. 18 hundredths: this would be
between 10 hundredths and 20 hundredths which would be the same thing as
between 1 tenth and 2 tenths. So 18 hundredths is going to be
someplace around here, so I definitely will not select that one. Let's try a few more of these. So they say "Write a decimal
that is equal to 24 tenths." Alright, 24 tenths. So remember
we could view this as-- I'll just write it down-- we could view
this as 20 tenths plus 4 tenths. But what is 20 tenths equal to? 10 tenths is equal to a whole, so 20 tenths is going to be
equal to 2 wholes. So this could be viewed
as 2 plus 4 tenths, or another way to write this--
we could just write 4 in the tenths place. So we could just write this as 2.4. 24 tenths: 20 tenths are 2 wholes
and then you have another 4 tenths. Let's do one other one. "102 hundredths." So we could rewrite this as
100 hundredths plus 2 hundredths. Now, what is 100 hundredths? Well 100 hundredths
is equal to 1, is equal to a whole. So 100 hundredths is just equal to 1. So you could view this as
1 plus 2 hundredths. Another way to write
two hundredths is 0.02. So what's 1 plus 0.02?
Well it's just going to be 1.02. And you see that here.
You have 1 and 2 hundredths. 1 is the same thing as 100 hundredths. So this is 100 hundredths
and you have 2 hundredths gives you 102 hundredths. Alright, let's do another one. "What is 32 tenths written as a decimal?" So we just have to remind ourselves:
10 tenths is equal to a whole. 20 tenths is equal to 2 ones.
30 tenths is equal to 3 ones. So this is going to be equal to 3 ones
and then another 2 tenths. 3 ones and another 2 tenths. Let's keep going. "What is 203 hundredths
written as a decimal?" Well we have to remind ourselves
that 200 hundredths is equal to 2 ones. So here this is the same thing as
2 ones and 3 hundredths. 2 ones-- this case right here--
2 ones and 3 hundredths. Let's do a couple more of these. "1.05 is equal to how many hundredths?" Well, one whole, or 1,
is equal to 100 hundredths. So this is 100 hundredths
plus 5 hundredths, or 105 hundredths. Alright. Let's do another one. "How can 2.60 be written in words?" So I could write this as 2 and 6 tenths.
2 ones and 6 tenths. I could also think of this as
2 ones and 60 hundredths. Or I could view this as 260 hundredths. So let's see which of these choices-- So "2 ones and 6 hundredths"... No, no, it's 2 ones and 60 hundredths,
not 6 hundredths. It's 6 tenths right over here.
6 tenths or 60 hundredths. I won't select that. "260 hundredths." Yeah, that's right because 2 ones
is that same thing as 200 hundredths and then we have another
60 hundredths right over there. So that's right. "260 tenths." No, 260 tenths--
remember 10 tenths is equal to a whole, so 260 tenths would be 26,
would be 26 ones. So it's not that choice either. So anyway, I think we've done
plenty of examples. Hopefully you have enjoyed that.