This Place Values Subtracting Large Numbers

Subtracting Large Numbers

Hey guys! Welcome to this video on subtracting large numbers.

I’m assuming you all know how to subtract smaller numbers, like 9 minus 2, at this point. Since, you are now venturing on to learn how to subtract large numbers.
Well, good news. It is the exact same method, the numbers just get harder to do in your head. So, learning helpful methods to subtract large numbers will help save you some trouble.
Let’s look at a few different examples.
We’ll start smaller.

   First:
27
-  9
____


Now, the first thing you need to make sure of, when subtracting large numbers, is that your number places are lined up correctly.
For instance, in our example here, 7 and 9 are in the same number place, so they need to be lined up directly across from one another.

When you try to subtract 9 from 7 that will give you a negative number, which we can’t have because we know 27 is bigger than 9. So, we need to borrow from our next place value. So, we need to subtract 1 from 2, leaving us with a 1 in the tens place, and bring that one we borrowed in front of our 7. Now, we have 9 being subtracted from 17. Which gives us 8, so we bring our 8 down. Again, being sure to keep it aligned with our ones places.
Now, we can imagine that there is a 0 to the left of our 9 here. Which means that we aren’t subtracting anything from the 1 we have left over here, so we can just bring that 1 down.

So, that gives us 18 as our answer.

Let’s try something a little harder.
Let’s take 567 and take 98 away from it.
So, don’t forget we need to line up our number places correctly.
Let’s line up our ones places together, and our ten places together.


567
- 98
_____


So, like in our last example we are trying to take something bigger away than what we have to take away. So, we need to borrow from our sweet neighbor 6. We are taking 1 away from 6, so let’s cross out our 6 and put a 5. Now, we can carry this 1 over in from of our 7. Now, we have 17 minus 8, which is 9. So, we bring that down to our ones place. Okay, now we are just dealing with our tens place. We only subtract numbers from their corresponding place values.

So, now we have 5 minus 9. Since 9 is more than what we can take from 5 we need to borrow from our hundreds place. So, we need to take 1 from 5 leaving us with a 4 in the hundreds place. We’ll carry that 1 in front of the 5 in our tens place giving us 15 minus 9. Which, is 6. So, we’ll carry that 6 down to the tens place (to the left of our 9 here). Since we aren’t taking anything away from our tens here, we can just carry our 4 down. Giving us 469 as our answer.

Now, for our last example let’s take a look at how to borrow across zeros. I’ll show you what I mean.
Let’s take 3,001 and take away 999 from it.
So, let’s set this up.


3,001
-  999
______


We, know we can’t take 9 away from one without making it a negative number, so we need to borrow. But, when we go to borrow one from our tens place we see there is nothing to borrow, because it’s a zero. Same case for the hundreds place. So, what we end up doing here is borrowing 1 from 300; leaving us with 299. Let’s cross out our 300 here, and write 299 above it. So, now we carry our 1 over here in front of the 1 giving us 11 minus 9, which is 2. So, we can carry that down. Then, we have 9 minus 9 which is zero.. And another 9 minus 9. We can carry those down.
We are left with a 2 in the thousands place, and we aren’t taking anything away from it, so we can just bring that down giving us 2,002 as our answer.

This borrowing works with all subtraction, just remember to only subtract numbers from their corresponding place values, and cross out and write the new number when you borrow.