Subtracting with place value blocks (regrouping)

What we want to do in this video is figure out what 438 minus 272 is. To help us think about that, we have these place value blocks right over here.

You can see 438: we have four hundreds (100, 200, 300, 400), we have three tens (one, two, three), and then we have eight ones. You can count those eight ones right over there. From that, we're going to take away two hundreds, so that's 200 right over there, seven tens or 70 right over here, and two ones. So pause this video and see if you can figure out what this is going to be.

Alright, now let's work through this together. First of all, we could start in the ones place, and we can see we have eight ones. Then we're going to take away two ones, so that's pretty straightforward; we're just going to be left with six ones right over here.

Now let's go to the tens place. The tens place is interesting: we have three tens here, and we're trying to take away from that seven tens. So, how do you take seven tens from three tens? Well, luckily we can regroup from the hundreds place. What if we were to take this piece right over here from the hundreds to the tens place? Now this is going to be the equivalent of ten tens.

Let me represent it that way. Once again, I took a hundred, and that's the same thing as one, two, three, four, five, six, seven, eight, nine, ten tens. Well, this is useful now because now I have ten plus three tens, or you could say I have thirteen tens. Now I can take away seven tens from that.

So let's do that: let's take away one, two, three, four, five, six, seven. What we are left with is six tens right over here. So now I have six tens left, six ones left, and then in the hundreds, I have three hundreds. I'm going to take away two of them, so I'm going to take away 100 and 200.

So, I'm left with just 100 there. I'm left with 100, six tens, and six ones. So this is one hundred, six tens, and six ones or one hundred and sixty-six.