Subtracting decimals: farmer's market
About this video
Omar takes $10 to the farmer's market and spends $8.79 on fruit. The video lines up the decimals, regroups across the zeros (ones to tenths to hundredths) to find that he has $1.21 left, then picks the picture that shows $1.21.
You'll be able to
- line up decimal numbers by place value to subtract money amounts.
- regroup across zeros when subtracting decimals.
- match a money amount like $1.21 to a picture of wholes, tenths and hundredths.
Key words
- regrouping
- Trading one unit of a bigger place value for 10 of the next smaller one, also called borrowing.
- tenth
- One of 10 equal parts of a whole; for money, one tenth of a dollar is 10 cents.
- hundredth
- One of 100 equal parts of a whole; for money, one hundredth of a dollar is 1 cent.
- place value
- The value a digit has because of where it is in a number, like ones, tenths or hundredths.
Transcript
- [Tutor] We're told, "Omar takes $10 to the farmer's market. He spends $8.79 cents on fruit. Which image represents how much money Omar has left?" So we'll pause this video and have a go at that before we do this together. Okay, so he takes $10 to the farmer's market, so that's how much he starts with, and I'll put the cents here as well.
And then he spends $8.79 on fruit, so we wanna subtract that out. And when I write the subtraction, we wanna make sure that we line up the place values. So the ones place below the ones place, the decimal below the decimal, $8.79 is what we're going to subtract, and so now let's start our subtraction.
So immediately when we go to the hundreds place, we see, well, we can't subtract nine from zero, we can't subtract in the 10th place, seven from zero, even in the one's place, how do we subtract eight from zero? So we're going have to do a little bit of regrouping, or some people might call it borrowing.
So let's take a 10 from the tens place and put it in the ones place, so a 10 is literally 10 ones, but we're not done yet, so because we have to worry about these zeros. So let's take one of those ones away, so we're now left with 9 ones, and that one that we took away, we're gonna regroup, that's equivalent to 10 tenths.
And then if we take one of those tenths away, that 10th is equivalent to 10 hundredths. And now we can subtract, 10 minus 9 is equal to 100th. Nine-tenths minus seven-tenths is two-tenths, we have our decimal right over here, and the 9 ones minus 8 ones is 1 one, so we get, he has $1.21 cents left.
So which image represents that? Well, Image A looks like just 21 cents, It's less than a dollar, so we'll rule that out. Image B, it's less than a dollar still, so let's just rule that out, So it should be Image C, and it does make sense because we have the $1 right over here, and then here, we have 20 cents, and then here, we have one more cent, we have one more cent.
Or another way to think about it is we have 21 of these hundreds filled in, so this is a dollar and 21, so I like Choice C.
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