Arithmetic (all content)
Subtracting decimals is simple when you line up the decimal points and fill in missing zeros. Regroup when needed by borrowing from the whole number and adding to the tenths place. Mastering this skill helps with everyday calculations and improves overall math understanding. Created by Sal Khan and Monterey Institute for Technology and Education.
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- Who invented decimals and fractions???(195 votes)
- The earliest recorded use of place value (writing numbers in a line to represent larger numbers) is from the ancient Babylonians around 1800 BC. However, they didn't have a decimal point, or a concept for zero yet. They just had to write the numbers out and determine how large it was based on context.
Bonus fact: The Babylonians used a base 60 numeral system, which is where we get our measurements of time from (60 seconds to a minute, 60 minutes to an hour)(194 votes)
- Why do you have to line up the decimals when you add or subtract?(57 votes)
- If you don't line them up, you may add ones to tenths, tenths to hundredths, etc. and get wrong answers. Lining them up helps you add or subtract all the proper places and get a correct answer.(23 votes)
- How do you borrow from nothing?.(12 votes)
- go to the next place up, but if you cant go up, you made a mistake and ordered your question wrong or you have to subtract it negatively(13 votes)
- Can you slow down...maybe.(7 votes)
- One thing you can do...
Go to the settings page in the bottom right hand side corner, and click the settings icon. There, you'll find a variety of settings including captions, playback speed, customizing captions, etc.
Click on the one that says "Playback Speed". There, you can adjust the speed to make Sal talk faster or slower than normal. It may be automatically set to 1x because that is the original amount. Making the x value smaller makes it slower, and making the x value larger makes it faster. NOTE: Most playback speeds have a maximum x value of 2x.
Hope this helps! -
Johnny Unidas(9 votes)
- this is easy(10 votes)
- why does this exist(6 votes)
- when your working with fractions if you get a number like 4.8 + 6.78 the .8 is basically 80 so it would be
6. 78(6 votes)
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We need to calculate 9.005 minus 3.6, or we could view it as 9 and 5 thousandths minus 3 and 6 tenths. Whenever you do a subtracting decimals problem, the most important thing, and this is true when you're adding decimals as well, is you have to line up the decimals. So this is 9.005 minus 3.6. So we've lined up the decimals, and now we're ready to subtract. Now we can subtract. So we start up here. We have 5 minus nothing. You can imagine this 3.6, or this 3 and 6 tenths, we could add two zeroes right here, and it would be the same thing as 3 and 600 thousandths, which is the same thing as 6 tenths. And when you look at it that way, you'd say, OK, 5 minus 0 is nothing, and you just write a 5 right there. Or you could have said, if there's nothing there, it would have been 5 minus nothing is 5. Then you have 0 minus 0, which is just 0. And then you have a 0 minus 6. And you can't subtract 6 from 0. So we need to get something into this space right here, and what we essentially are going to do is regroup. We're going to take one 1 from the 9, so let's do that. So let's take one 1 from the 9, so it becomes an 8. And we need to do something with that one 1. We're going to put it in the tenths place. Now remember, one whole is equal to 10 tenths. This is the tenths place. So then this will become 10. Sometimes it's taught that you're borrowing the 1, but you're really taking it, and you're actually taking 10 from the place to your left. So one whole is 10 tenths, we're in the tenths place. So you have 10 minus 6. Let me switch colors. 10 minus 6 is 4. You have your decimal right there, and then you have 8 minus 3 is 5. So 9.005 minus 3.6 is 5.405.