Dividing a Decimal by a Power of 10

u3_l2_t2_we4 Dividing a Decimal by a Power of 10

We are asked to divide 99.061 or

ninety nine and sixty one thousandths by 100.

And there is a few ways to do it

but all I'm going to do in this video is focus on

kind of a faster way to think about it.

And hopefully it will make sense to you.

And that is also the focus of it. That it makes sense to you.

Let us just think about it a little bit.

So 99.061. So if we were to divide this by 10,

just to make the point clear,

if we were to divide this by 10, what would we get?

Well, we would essentially move the decimal place

one spot to the left. And it should make sense

because we have a little over 99.

If you took 99 divided by 10, you should have a little over 9.

So essentially you would move the decimal place

one to the left when you divide by 10.

So this would be equal to 9.9061.

If you were to divide it by 100,

which is actually the focus of this problem,

so if we divide 99.061 divided by 100.

If we move the decimal place once to the left,

we're dividing by 10.

To divide it by 100, we have to divide it by 10 again.

So we move it over twice. So one, two times.

And so now the decimal place is out in front of that first leading 9.

Which also should make sense. 99 is almost 100.

Or a little bit less than 100. So if you divide it by 100

we should be a little bit less than 1.

And so if you move the decimal place

two places over to the left,

because we're really dividing by 10 twice

if you want to think of it that way,

we will get the decimal in front of the 99.

.99061, we should put a 0 out here,

just sometimes it clarifies things.

So then we get this right over here.

Now one way to think about it,

although I do want you to always imagine that

when you move the decimal place over to the left,

you really are dividing by 10 when you move it to the left.

When you move it to the right, you are multiplying by 10.

Sometimes people say, hey look,

you could just count the number of zeros.

And if you are dividing, so over here you are dividing by 100,

100 has two zeros, so when we're dividing by it,

so we can move our decimal two spaces to the left.

That's alright to do that, if you know

especially if it's kind of a fast way to do it.

If this had 20 zeros, you would have needed to say,

ok, let us move the decimal 20 spaces to the left.

But I really want you to think about why that's working.

Why that makes sense?

Why it's giving you a number that seems to be

in the right kind of size number.

That this is why it makes sense that

if you take something that's almost 100

and divide it by 100, you'll get something that's almost 1.

And that part, frankly, is just a really good reality check

to make sure you're going in the right direction with the decimal.

Because if you were to try this five or ten years from now,

maybe your memory of the rule

or whatever you want to call it for doing it,

you're like, hey, wait. Do I move the decimal

to the left or the right?

It's really good to do that reality check

to say, ok, look. If I'm dividing by 100,

I should be getting a smaller value.

And that moving the decimal to the left

gives me that smaller value.

If I was multiplying by 100, I should get a larger value.

And moving the decimal to the right

would give you that larger value.