## Multiplying a Decimal by a Power of 10

• 0:01 - 0:08
A single postage stamp costs \$0.44. How much would a roll of 1000 stamps cost?
• 0:08 - 0:12
And there is really a couple of ways to do it, and I'll do it both ways just to show you they both work.
• 0:12 - 0:15
One is a kind of a faster way, but I want to make sure you understand why it works.
• 0:15 - 0:18
And then we'll verify that it actually gives us the right answer
• 0:18 - 0:21
using maybe the more traditional way of multiplying decimals.
• 0:21 - 0:27
So, we're starting at \$0.44. I'll just write a 0.44.
• 0:27 - 0:32
Well, that's one stamp, so this is one stamp. I'll write it like this, 1 stamp.
• 0:32 - 0:34
How much would 10 stamps cost?
• 0:34 - 0:37
Well, if 1 stamp is \$0.44, then 10 stamps,
• 0:37 - 0:40
we could move the decimal to the right one place,
• 0:40 - 0:44
and so it would be, and now this leading zero is not that useful,
• 0:44 - 0:52
so it would now be \$4.4. Or if you want to make it clear, it would be \$4.40.
• 0:52 - 0:56
Now, what happens if you want to have a hundred stamps? 100 stamps.
• 0:56 - 0:58
Well, the same idea is going to happen.
• 0:58 - 1:03
We're now taking 10 times more so we're going to move to the decimal to the right once.
• 1:03 - 1:07
So, a hundred stamps are going to cost, are going to cost \$44.00.
• 1:07 - 1:09
And this should make sense for you.
• 1:09 - 1:16
If one stamp is 44 hundreths of a dollar, then a hundred stamps are going to be
• 1:16 - 1:21
44 hundreths of a hundred dollars, or \$44. Or you could view it as
• 1:21 - 1:23
we've just moved the decimal over one place.
• 1:23 - 1:26
So if we want a thousand stamps, if we want 1000 stamps,
• 1:26 - 1:28
we would move the decimal to the right one more time.
• 1:28 - 1:35
Moving the decimal to the right is equivalent to multiplying by ten. So then it would be \$440.
• 1:35 - 1:41
Now, we could put, add another trailing zero just to make it clear that there is no cents over here.
• 1:41 - 1:44
So if you want to do it really quickly, you could've started with \$0.44.
• 1:44 - 1:48
And you say, look, I'm not multiplying by ten. I'm not multiplying by a hundred.
• 1:48 - 1:53
I'm multiplying by a thousand. You're going to have to put another trailing zero over here.
• 1:53 - 1:59
And you would move the decimals from over here to over here.
• 1:59 - 2:05
You've essentially multiplied this times ten times ten times ten, which is a thousand.
• 2:05 - 2:10
So then this would become \$440.
• 2:10 - 2:15
So let's verify that this works the exactly the same if we multiply the traditional way
• 2:15 - 2:25
the way we multiply decimals. So if you have 1000 times \$0.44.
• 2:25 - 2:33
So you start over here. 4 times 0 is 0, 4 times 0 is 0, 4 times 0 is 0, 4 times 1 is 4.
• 2:33 - 2:36
Or you could just say, hey, this was 4 times a thousand.
• 2:36 - 2:40
Then we're going to go one place over so we're going to add a zero.
• 2:40 - 2:48
And we, once again, we're going to have 4 times 0 is 0, 4 times 0 is 0, 4 times 0 is 0, 4 times 1 is 4.
• 2:48 - 2:51
Or we just did 4 times a thousand. So that is 4000,
• 2:51 - 2:54
if you don't include this zero that we added here ahead of time
• 2:54 - 2:57
because we're going one place to the left.
• 2:57 - 3:01
And then we have nothing left. I haven't at all thought about the decimals right now.
• 3:01 - 3:06
So far I've really just viewed it as a thousand times 44. I've been ignoring the decimal.
• 3:06 - 3:08
So if it was a thousand times 44,
• 3:08 - 3:15
we would get 0 plus 0 is 0, 0 plus 0 is 0, 0 plus 0 is 0, 4 plus 0 is 4,
• 3:15 - 3:19
4 plus nothing is 4. And if you ignore the decimal, that makes a lot of sense.
• 3:19 - 3:24
Because a thousand times 4 is 4000 and a thousand times 40 would be 40 000.
• 3:24 - 3:31
So you would get 44 000. But this of course is not a 44. This is a 44 hundreths.
• 3:31 - 3:34
We have, between the two numbers, two numbers behind the decimal point.
• 3:34 - 3:38
So we need to have two numbers behind or to the right of the decimal point in our answer.
• 3:38 - 3:41
So one, two. Right over there.
• 3:41 -
So, once again, we get \$440.00 for the thousand stamps.
Title:
Multiplying a Decimal by a Power of 10
Description:

u3_l2_t2_we2 Multiplying a Decimal by a Power of 10

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Video Language:
English
Duration:
03:47 clairedevir3 edited English subtitles for Multiplying a Decimal by a Power of 10 clairedevir3 edited English subtitles for Multiplying a Decimal by a Power of 10 sweety.revathi22 edited English subtitles for Multiplying a Decimal by a Power of 10 Taylorr added a translation

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