Before we move on, I just want to make sure you have deep understanding of how we actually computed 600, that’s not what I wanted to do, 600 why is pen malfunctioning. Let's see 698, no, that’s not the word, not only is my pen malfunctioning my brain is as well, 686 minus 298. And I drew out the place values and everything last time but I want to show you that you don’t have to do that but you can still have the exact same intuition. So the way you should do this type of problem in a few videos were going to start doing this four digit numbers and that’s why I want to make sure you understand it properly with three digit numbers. Is you and you know and the way I did last time, I said “Oh, well, you know, first I have subtract into ones place and I have an eight here and that six years, so let me get some 10 from the 10th place and then, you know, this became but what I want to show you is you can actually do all of the regrouping or all of the barring depending on how you want to call it, all though I like to call it taking ahead of time rather than borrowing because you don’t give it back.

So how do we think about it? So in order to do any subtraction problem you just have to make sure that the number on top is bigger than the number on the bottom, right. So for example in the hundreds place here and were not going to negative numbers yet, just yet, we’ll you'll learn that in the couple of years of you're specially advanced maybe even faster. But we see here that in the hundreds place, this number is lower than this number so that’s cool. But then it would have go the 10th place what happens here, this nine which represents 90 that’s bigger than this eight which represents 80, right. So how can we subtract 90 from 80 and you’ll learn later that I don’t give you a negative number and all of that but we want to stay in positive number so we have to have a number larger than 90 here we only have 80, we have eight to tenths.

So what we can do is we have 600 right here, right this six represents 600. So let's take one of them, so we’ll take, so we’ll take one of the six hundreds and were left with just five hundreds but now we have a hundred to play with. And let's put those hundreds in the tenth place. Well a hundred is how many tens, a hundred is 10 tenths, right. So if we add a 100 to 80 we get what we get a 180 but if we write that as tenths that 18 tenths. So this becomes 18 tenths, right. Let me and I really want you to understand I don’t want you to just do this mechanically, I really want you to understand what's going on here.

When we took, when we took this six and turn into a five we took one from the hundreds place, one from the hundreds place represents 100. So when you take that hundred and represent it in the tenths place it becomes 10 tenths right. 100 is 10 tenths so we have eight tenths and we add 10 tenths to it, so then you get 18 tenths, right, that one—all I'm saying is that 100 becomes 10 tenths, right. 10 times 10 is a 100 and we added those 10 tenths to the eight tens that we already had here and we got 18. So now the five is greater then the two, 500 is greater than 200. 18 tens or a 180 is greater than nine tenths or 90 but in here we have six is smaller than eight so were not done yet.

So what can we do? How can we add more ones here? Well we could a ten from here we could take a ten from here and then put it into the ones place. So let's a take a 10 away, so we're going to take a 10 here, so we only have 17 tenths left, right because this is the tenths place. So one ten is equal to—all right, you could almost see this as a $10.00 bill right. We have 18 $10.00 bills and now we took one of those $10.00 bills and we have 17 and so that equals one—and that equal 10 ones, right. A $10.00 bill is equal to $1.00 bills. And so we took one tenth from here and then we could put it into the ones place. So we have 10 more ones, so then this becomes well we had six or so you know, you could say $6.00 and now we're going to add 10 to it, so we're going to have 16. You may have learned you know before that you're taking a one and you could put the one to the eight but why is that really happening because you took a one from here but that one is a hundred which represents 10 ones—that, sorry, that one is a hundred so it represents 10 tenths.

So 10 tenths plus eight that was 18 tenths and then similarly we took a 10 from here and so we have 17 tenths and then we took that one tenth turn into 10 ones and add to the six. I'm probably confusing you but hopefully you're getting the intuition. So now, we're on a situation where the five is greater than the two, the 17 is greater than the nine and the 16 is greater than the eight and so we're ready to subtract and we could do it any direction we want to, we could start from the left and go to the right, we could start from the right go to the left. Let's, I don’t know, since it's a little conventional start from the left what's 500 minus 200 well that’s 300, right because we're in the hundreds place. What's 17 tenths minus nine tenths so that’s the same thing as a 170 minus 90 right. Well that’s 80 or eight tenths or you could say 17 minus nine is eight.

And then finally what is 16 minus eight, well that’s just eight. So there you have it that was a problem we just did and hopefully that clarified things a little bit. So let's move to the next problem. So problem number five and on the same page is taken me 20 minutes just to stay on the same page. A man an unnamed man, that’s kind of suspicious. A man sold 230 balloons at a carnival in the morning. That’s kind of unimportant information we don’t have to know that was at a carnival in the morning that’s just there to confuse you. So I'm just going to write that a man sold 230 balloons and I don’t care where he sold it or what time he sold it. He had then says, he sold another 86 balloons in the evening. Ones again I don’t care where I will say it, so this was in the morning and evening.

The question they ask us is how many balloons did he sell at all? How many did he sell in all? well if he sold 200—let's say in the morning which I didn’t write down but let's say that this—and a man sold 230 balloons in the morning, so that’s that part of the statement so we could represent it with this Singapore math bars that they like to do. So let's say that that’s, that has length of 230 and the units here balloons maybe that should be another unit of length the balloon. That’s 230 and then it says he sold another 86 in the evening, he sold, sold another 86 in the evening. So let's use one of this Singapore math bars. So he sold another 86, just maybe it looked something like that, so he sold another 86 in the evening. And they want to know how many did he sell in all? So how many did he sell in all?

We pick a new color, how many did he sell in all? It was going to be this number that he sold in the morning plus the number he sold in the evening. It's going to be this whole length so it's essentially going to be the sum of 230 and 86. So 230 and 86 and the total number balloons he sold, so 230 plus 86 that h should be right below the three. So okay, let's add the ones place so zero plus six, so that’s six ones, right. Zero ones plus six ones is six ones. So three tenths plus eight tenths right because we're in the tenths place that equals 11 tenths, right. But 11 tenths we can't write it, we can write a 11 right here in the tenths place. So what we do is, so you know, this three, this three plus eight that’s the same thing as 30 plus 80 right because we're in the tenths place.

And we know 30 plus 80 you know that equals 11 tenths and equal to 110. But we can't write, we can't write 11 here, 11 is not a digit, so what we could do is we could take a hundred of this and turn it—and turn it into one. So this is you could read as a 100 plus 10, right. Or you could view it one in the hundreds place and a 10, so what we can do let's just put the one tenths down here and then the hundreds place and you might have learned this is you know carry the one put it up here, right. Kind of you know when I was learning math in elementary school they would say “Oh, three plus eight is 11” so put the one down carry the one. But essentially what you're doing, you're saying 30 plus 80 is a 110. And a 110 is one hundred and one tenth. So we're putting the 10 down here because that’s the tenths place and then the hundred we're adding to the hundreds place so that’s what's carrying the one really is. And I want you to have that intuition.

All though you know if you just carry the one it's fairly easy, three plus eight is 11 carry the one. And now we have a one in the hundreds place this is a hundred plus a 200 that equals 300, so 316 that’s how many balloons that unnamed man sold in all at the carnival. I will see you in the next video.