So slightly off-topic... I quit marijuana recently, and as I do these exercises and get further into Khan Academy, I keep wondering if people can do these exercises easily in their head. Give me a pen and paper and these problems are like nothing, because I understand them conceptually, but in my head I can barely keep track of the answers generated at each step. Just curious if I'm the only one that needs a pen and paper for this simple stuff.

Some people can do these kinds of things in their heads, but don’t beat yourself up if you can’t. It gets easier with practice and as you find your own shortcuts. :)

I now how to do it but I can't do it sideways I now it doesn't mater if it is sideways or not

Do it the way that makes it easier for you...but sometime in your life you will have to learn it sideways

so when you line up all the numbers will you subtract left to right or the other way around??

Like any regular subtraction problem, you will subtract right to left.

do we have to line it up exactly?

You cant take a hundredth away from a 10th and vice versa. Think of fractions: you can't subtract 3/5 - 1/3, you need a common denominator. The same thing with decimals. So we subtract hundredths from hundredths, and tenths from tenths. And when you don't have enough hundredths, you borrow 10 hundredths from the tenths (1/10=10/100). So once you line it up, it's the same as any other subtraction problem, just with a decimal in the middle.

if I go on youtube and search this will this vid come up? Or is it only on the site?

did you know that this is on the site and on youtube too

What is "standard algorithm"?

It is the standard or original way to do the math, like dividing or multiplying.

I don't understand this concept on the video

Try to do the problems without the decimals first and then try to put them back and do them. It should still all work the same way. The only difference is that the numbers that are to the right of the decimal are just showing that they are units but they are not enough to create 1 whole unit.

Main content

5th grade

Course: 5th grade > Unit 3

Lesson 3: Subtracting decimals (hundredths)

Subtracting decimals: 9.57-8.09

Name: Subtracting decimals: 9.57-8.09
Uploaded: 2013-12-27T22:16:42Z
Description: To find the least common denominator of two fractions, we can either list out the multiples of the two denominators until we find a common one, or use prime factorization. Once we've found the least common denominator, we can rewrite the fractions so they both have this denominator, and then add them together.

CCSS.Math:

5.NBT.B.7

Google Classroom

To find the least common denominator of two fractions, we can either list out the multiples of the two denominators until we find a common one, or use prime factorization. Once we've found the least common denominator, we can rewrite the fractions so they both have this denominator, and then add them together. Created by Sal Khan.

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eye_travis
Posted a year ago. Direct link to eye_travis's post “So slightly off-topic... ...”
So slightly off-topic...

I quit marijuana recently, and as I do these exercises and get further into Khan Academy, I keep wondering if people can do these exercises easily in their head. Give me a pen and paper and these problems are like nothing, because I understand them conceptually, but in my head I can barely keep track of the answers generated at each step.

Just curious if I'm the only one that needs a pen and paper for this simple stuff.
Button navigates to signup pageComment on eye_travis's post “So slightly off-topic... ...”
(8 votes)
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- Johanna
  Posted a year ago. Direct link to Johanna's post “Some people can do these ...”
  Some people can do these kinds of things in their heads, but don’t beat yourself up if you can’t. It gets easier with practice and as you find your own shortcuts. :)
  Comment on Johanna's post “Some people can do these ...”
  (7 votes)
ProJorden💎🦄💎🐢🐢🐢🐢🐢🐢
Posted 9 years ago. Direct link to ProJorden💎🦄💎🐢🐢🐢🐢🐢🐢's post “I now how to do it but I ...”
I now how to do it but I can't do it sideways I now it doesn't mater if it is sideways or not
Button navigates to signup pageComment on ProJorden💎🦄💎🐢🐢🐢🐢🐢🐢's post “I now how to do it but I ...”
(2 votes)
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- Toby Harris
  Posted 3 years ago. Direct link to Toby Harris's post “Do it the way that makes ...”
  Do it the way that makes it easier for you...but sometime in your life you will have to learn it sideways
  Button navigates to signup page
  (3 votes)
🤨📸📸📸📸📸📸📸📸📸
Posted a month ago. Direct link to 🤨📸📸📸📸📸📸📸📸📸's post “khan academy Incredible A...”
khan academy Incredible Answer%
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(2 votes)
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EFHaas05😂
Posted 9 years ago. Direct link to EFHaas05😂's post “so when you line up all t...”
so when you line up all the numbers will you subtract left to right or the other way around??
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(2 votes)
Answer
- Johnson
  Posted 9 years ago. Direct link to Johnson's post “Like any regular subtract...”
  Like any regular subtraction problem, you will subtract right to left.
  Comment on Johnson's post “Like any regular subtract...”
  (3 votes)
JosiahRamesar
Posted 9 years ago. Direct link to JosiahRamesar's post “Great video and now I rea...”
Great video and now I really now how to subtract decimals. Thank you?
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(2 votes)
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summer
Posted 8 years ago. Direct link to summer's post “do we have to line it up ...”
do we have to line it up exactly?
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(1 vote)
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- T G
  Posted 8 years ago. Direct link to T G's post “You cant take a hundredth...”
  You cant take a hundredth away from a 10th and vice versa. Think of fractions: you can't subtract 3/5 - 1/3, you need a common denominator. The same thing with decimals. So we subtract hundredths from hundredths, and tenths from tenths. And when you don't have enough hundredths, you borrow 10 hundredths from the tenths (1/10=10/100). So once you line it up, it's the same as any other subtraction problem, just with a decimal in the middle.
  Button navigates to signup page
  (2 votes)
FieldsJaden
Posted 9 years ago. Direct link to FieldsJaden's post “if I go on youtube and se...”
if I go on youtube and search this will this vid come up? Or is it only on the site?
Button navigates to signup pageComment on FieldsJaden's post “if I go on youtube and se...”
(1 vote)
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- EzekielTweneboah
  Posted 9 years ago. Direct link to EzekielTweneboah's post “did you know that this i...”
  did you know that this is on the site and on youtube too
  Comment on EzekielTweneboah's post “did you know that this i...”
  (2 votes)
Azure Lewis
Posted 7 years ago. Direct link to Azure Lewis's post “I don't understand this c...”
I don't understand this concept on the video
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(0 votes)
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- noabobo
  Posted 7 years ago. Direct link to noabobo's post “Try to do the problems wi...”
  Try to do the problems without the decimals first and then try to put them back and do them.
  It should still all work the same way. The only difference is that the numbers that are to the right of the decimal are just showing that they are units but they are not enough to create 1 whole unit.
  Comment on noabobo's post “Try to do the problems wi...”
  (4 votes)
@khanacademyuser
Posted 3 years ago. Direct link to @khanacademyuser's post “What is "standard algorit...”
What is "standard algorithm"?
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(1 vote)
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- Aditi
  Posted 3 years ago. Direct link to Aditi's post “It is the standard or ori...”
  It is the standard or original way to do the math, like dividing or multiplying.
  Button navigates to signup page
  (2 votes)
jacqueline.granados
Posted 8 years ago. Direct link to jacqueline.granados's post “i dont get this it dosent...”
i dont get this it dosent give me move edvice
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- Aditi
  Posted 3 years ago. Direct link to Aditi's post “What do you not get? Mayb...”
  What do you not get? Maybe if you have a different math resource, maybe you should go to that. I don't get all my questions answered on khan academy either.
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  (0 votes)

Video transcript

Let's try to subtract 9.57 minus 8.09. So try to pause this video and figure this out first before we work through it together. All right. Well, let's just rewrite it. Let's rewrite it. And when I rewrite it, I like to line up the decimals. This one it's a little intuitive. We have 8.09. Just like that, and now we're ready to subtract. And we want to subtract 9 hundredths from 7 hundredths. Well, we don't have enough hundredths up here so let's move over here. Let's see if we can do some regrouping so we always have a higher number on top. So over here we want to subtract 0 tenths from 5 tenths so we have enough tenths over here. So let's regroup. So instead of 5 tenths, I'm going to have 4 tenths, and then I'm going to give that other tenth, which is the same thing as 10 hundredths over here, so this becomes 17 hundredths. 17 minus 9 is 8. 4 minus 0 is 4. And then I have 9 minus 8 is 1. So this is going to be 1.48.