- [Teacher] Hello.
Today we're going to talk about rounding
using the vertical number line.
We have previous where we learned to round
by tens and by hundreds using
the vertical number line.
Today we're going to see what happens
when we have a number
that needs to be rounded
both to the hundreds and the tens.
Okay. So we're going to set up
our two vertical number lines.
This will be our tens,
and this will be our hundreds.
Lets come up with a number, lets see.
How about
643.
Okay, so I'm going to put
my tens, the ten below.
So the ten below 643
would be 640.
The ten above would be 650.
In the middle is 645.
So notice that even
though I have hundreds,
I can still label it with the
ten below and the ten above.
For the hundreds,
the hundred below is 600,
and the hundred above is 700.
Right in the middle is 650.
Okay, so we're using the same number
but we have different marks
on our number lines.
Okay, now I need to place my number, 643.
Well, here's
40,
41,
42,
43,
44.
So 43 would go right there, 643.
Here, I have 600 to 650.
643 is almost at 650
so I'll put it right here.
It would be too hard to count
by ones between zero and 50
so I just estimate for this one.
Now it's clear to see here on the hundreds
that 643 is closer to 600
than it is to 700.
It's also below 650, which shows me that
643 rounded to the nearest
hundred would be 600.
Lets go back to our tens.
Notice that 643 is closer to 640
than it is to 650.
It's also below 645,
so I know that 643 rounds to 640.
So that's how we can round the same number
to both tens and hundreds
using the vertical number line.
Thanks for watching,
I'll see you next time.
