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## Early math review

### Course: Early math review > Unit 5

Lesson 8: Subtraction within 100# Subtracting with regrouping (borrowing)

Sal subtracts 25 from 83 by thinking about tens and ones.

## Want to join the conversation?

- Does regrouping also apply to subtracting 3- or 4-digit numbers?(67 votes)
- Yes it does! :) It is the same as subtracting two digits, except there are more numbers.(76 votes)

- So regrouping and borrowing are the same thing?(5 votes)
- Yes they are the same thing. Margaretz is incorrect. The title of the video is subtracting with regrouping (borrowing) neither regrouping or borrowing belongs to addition or subtraction.(4 votes)

- How do you solve 48-77=? i always get -31 as answer though it should be -29(5 votes)
- What you can do is reorder them, then subtract them like normal, then 'flip' the answer.
`77-48 = 29`

then put a minus on the`29`

to make it`-29`

and there's your answer!

By the way, I'm not too sure about this way, but try it and see if it works for you!(6 votes)

- do you know what 23-18=?(3 votes)
- The answer to 18 subtracted from 23 is 5(3 votes)

- that makes alot of sence wow i didn't get it until just now lol(6 votes)
- Is there a video for subtracting a bigger number from a smaller number? I need a little help with my homework...(3 votes)
- Hi Miraculous Ladybug,

When subtracting a bigger number from a smaller number, something like this should be seen:

5-7 = ?

When a bigger number is subtracted from a smaller number, the value that you get from that equation will be*negative*.

A number line looks something like this:

<*__l___l___l___l___l___l___l___l___l___l___l___l___l__*>

-3 -2 -1 0 1 2 3 4 5 6 7 8 9

When you subtract seven from five, you're subtracting seven "ones" from five, which will lead to negative two.

Hope this helped, and good luck on your math!(7 votes)

- What do you do if you can't regroup since the place to the left is a 0?(3 votes)
- it would be zero of something, like 20, 2 tens and 0 ones.(5 votes)

- What if the last two numbers that you're subtracting ( so like 253-342), how would you regroup 2 and 3? because that would change the whole thing that you're doing(7 votes)
- Can we borrow if we have an equation like this? 367

-635 = ?(5 votes)- No since you are taking away more then what you have. In this case subtract 635-367 and make the answer negative. The answer is = -268. Negative means your answer is less than zero.(2 votes)

- why is regrouping important(3 votes)
- HI Vivian!

I'm a big twilight fan to!!

Anyway regrouping helps math look like it has some type of sense we really have to admit we don't like math but once you understand how regrouping helps make the run more smoothly you will see how regrouping is important.(2 votes)

## Video transcript

- [Voiceover] So let's see
if we can subtract 25 from 83 or if we can figure out
what 83 minus 25 is. I encourage you to pause the video and see if you can work through it. So I'm assuming you've had a try. And when you try to work through it, you probably first went to the
ones place right over here. And you probably said, "Hey,
I have three ones on top "and from that I want
to subtract five ones." But you said, "Wait, I can't subtract "five ones from three ones. "Five is more than three. "What do I do?" And what you do is what
I'm about to show you. You do something called regrouping. You take some of the value
that's in the tens place and put it into the ones place. What am I talking about? I'm gonna do it three different ways. So you really hopefully
understand what's going on. Well, you want this three to be more ones. You want it to be at least
as large as five or larger. So how do you do that? Well you could take a
10 from the tens place. So instead of having eight tens here, you could take one of them away and then you're going
to have seven tens here. And then if you take a 10, you could just put 10 away from here. You put in the ones place,
that's going to be 10. So 10 plus three is 13. 10 plus three is 13. So what did I do again? 83 is eight tens and three ones. You could also think of it
as seven tens and 13 ones. And I'm going to do it again in a couple of different ways to make that clear. But let's just work through this now because now you have
13 ones minus five ones which is going to be eight ones. And then you go to the
tens place and you say, "Seven tens minus two tens, "well that's going to be five tens." So your answer is going to be five tens and eight ones or 58. Now I said I would do this several ways so that it makes a little bit
more sense so let's do that. So another way that you could write 83 is you could write this, this is the same thing as 80 plus three. 80 plus three. That's the same thing as 83. Eights tens, three ones,
eight tens, three ones. And 25 is the same thing as 20 plus five. 20 plus five. Now we're going to subtract 20 plus five. So let's write this instead as... We're going to subtract 20. We're going to subtract two tens and we're going to subtract five ones. So subtracting 25 is the same thing as subtracting 20 and
then subtracting five. So now let's try to work
through it just like we did. Well we go to the ones place again. Ones again was a five. If I want to take five away from three, that's hard, I don't know
how to do that just yet. But what if I take ten from here? So if I take a 10, if
I take 10 from there, that's going to be 70. And if I put that 10 in the ones place, well 10 plus three is going to be 13. Notice, I haven't changed
the value of the numbers. 70 plus 13 is the exact same thing as 80 plus three which is 83. But what's useful about this is now, in the ones place, I can
subtract five from 13. If I subtract five from
13, I'm gonna get an eight. And then if I subtract
two tens from seven tens or 20 from 70, I'm going to get 50. I'm going to get 50. So this is going to end
up being 50 plus eight which is the exact same thing as 58. Five tens and eight ones. Now I said I would do the third way. And these are all the same way. I'm just writing it
down in different ways. So I could also write 83. I could write this down as eight tens plus three ones. All right, this is the tens place. This is the ones place. Eight tens, three ones. I'm gonna subtract two tens and five ones. So I could write... So this is going to be minus two tens and minus three ones. I'm sorry, and minus five ones. Minus five ones. 25 is the same thing as 20 and five. If I'm subtracting 25,
that's the same thing as subtracting 20 and
then subtracting five. And that's the same thing as subtracting two tens and then subtracting five ones. Two tens and five ones. So let's then work this out. So this is going to be... Well, as soon as we try
to subtract five ones from three ones, we say,
"It doesn't make any sense." Let me make the value here larger. And I'm gonna do that by
regrouping from the tens place. Instead of writing this as eight tens, I'm gonna take one of those tens away. I'm gonna write it as seven tens. And then put that 10 in the ones place. Well one 10 is equal to 10 ones. So if I added it to the three,
this is going to be 13 ones. And now I can subtract. 13 ones minus five ones is eight ones. And seven tens minus
two tens is five tens. Five tens. We are done. These are all different ways of doing the exact same problem with regrouping.