Relating money to decimals
The narrator calls the non-matching hundredths-grid model 'D', but it is the third model he discusses, and he then corrects himself to 'an answer'. The models are shown only on screen, so the interventions describe them in words and don't use letters.
The check-ins use the correct version. The video is Khan Academy's, unchanged.About this video
The video checks four models to see which ones show 3.45, or $3.45. A fraction (345/100), a set of coins and bills, and another set of coins all show 3 wholes and 45 hundredths. The hundredths-grid model shows 3.50, so it is the one that does not match.
You'll be able to
- show 3.45 as a fraction, as money and with place value parts.
- count coins and bills to check if they make a given decimal amount.
- read a hundredths grid model and spot one that does not match.
Key words
- hundredths
- Parts of a whole split into 100 equal pieces; one cent is one hundredth of a dollar.
- tenths
- Parts of a whole split into 10 equal pieces; 4/10 is the same as 40/100.
- hundredths grid
- A 10 by 10 square where each small square is one hundredth of a whole.
- model
- A picture, set of objects or numbers that shows an amount in a different way.
Transcript
- [Instructor] We're told, Justine shows her friend different ways to model 3.45, or I guess I'm seeing money here, so maybe it's $3.45, or 3 wholes and 45/100, or 3 wholes, 4/10 and 5/100, however you wanna think about it. Which of the following could be the models Justine showed?
And it says choose three answers. So really three of these are going to be right and one of them is going to be wrong. They could have just said pick the one that does not model it. But anyway, (laughs) let's just go through it. I'll pause this video, have a go at it before we do this together.
All right, now let's do this together. So this right over here, 345 over 100, we could rewrite this over here as 300 over 100 plus 45 over 100. Well, 300/100, this is the same thing as three wholes. So this is 3 wholes and 45/100. If I wanted to write that as a decimal, it would be 3 wholes and 45/100.
I could also write this if I want, I could rewrite that 45/100, 45 over a hundred is equal to 40 over a hundred plus 5 over 100, and that's equal to 40 over a hundred is the same thing as 4/10, and then I have 5/100. And that's what we also have here. We have three wholes, 4/10, and 5/100.
So I like this answer right over here. Now let's look at this one. I have $3, I could give you those as the three wholes. And then, let's see, I have a quarter, that is 25 cents, a dime, this is 10. And it looks like those are two nickels. So that's five and five.
So if I were to add these together, see, 5 plus 5 is 10 plus 10 is 20, plus 25 is 45. So this looks like three wholes and 45/100, or $3 and 45 cents. So I like this one as well. Now this one, it looks like each of these is split into hundredths, 'cause it's a 10 by 10 grid.
So this is a whole, two wholes, three wholes. So so far it's looking good. That's three wholes. And then what's this? Well, this doesn't look like 45/100. It's exactly half of the hundreds here. This is 50 over a hundred. This right over here is 50 over a hundred.
So I would represent this as 3.5 or 3 and 50 hundreds. It's not three and 45 hundreds, so this is not our choice. So D is probably going to be the answer, but let's double check this, or it's going to be an answer. So I have two wholes here, so this is gonna be an answer if this all adds up to another whole and 45 cents.
So let's see, I have 25, 25, 25, those are the quarters. And then I have a bunch of dimes here. 10, 10, 10, 10, 10. And then I have these nickels here. Five, five, five, and five. And what I'm going to do is, let's see, how do I make a dollar? If I had four quarters, I could make a dollar.
I don't have four quarters, but if I have these three quarters, which is 75 cents, and then I add another 25 cents, that right over there is another whole. And then what do I have left over? I have 5, 10, 15, plus 30 is 45. So this right over here is 45 cents.
So I have one whole, sorry, I have two wholes, three wholes, and 45 cents. So that's why I like this choice as well.
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