Dividing 3-digit numbers by 2 digit-numbers | Grade 5 (TX TEKS) | Khan Academy

Let's get a little bit more practice dividing. So let's say we want to figure out what 868 divided by 28 is. Pause this video and see if you can figure that out.

All right, now let's work through this together. So we're going to take 28, we're going to divide it into 868. The first thing I would do is try to estimate how many times would 28 go into 86. Let's see, 28 is a little bit less than 30, and 86 is a little bit less than 90. 30 would go into 90 about three times, so let me try three here.

So let me put a three there, and let's figure out what 3 * 28 is. 3 * 8 is 24, and then 3 * 2 is 6 + 2 is 8. Looks like I did that right; I just got right below it. I didn't go over it. Here, 86 - 84 is 2. Bring down this eight right over here, and let me get rid of that so it doesn't confuse me.

How many times does 28 go into 28? Well, that one's pretty straightforward: it goes exactly one time. 1 * 28 is 28, and I'm done. I'm left with no remainder.

Let's look at another example here. Let's say we wanted to figure out what 724 divided by 53 is. Pause the video and have a go with that.

All right, so we have 53. We're trying to figure out how many times does it go into 724. So first estimating how many times does 53 go into 72? Well, it goes at least once. It doesn't go twice because that would be over 100, so let me just put a one here. 1 * 53 is 53.

Now let me subtract. You might be able to do this in your head. You might say, "Okay, 73 minus 53 would be 20," but this is 72, so it'd be 19. But let's just do this with regrouping just to make sure we're doing it well.

So let's see, I can take 10 from here, so that becomes a six, and I give that 10 to this two, so it becomes a 12. 12 - 3 is 9, 6 - 5 is 1, and now let me bring down this four. So I'm trying to figure out how many times does 53 go into 194.

So see, 50 would go into 200. I'm just estimating by rounding to the nearest, well, in this case, rounding to the nearest 100. But let's see if I—50 goes into 200 about four times, but this is less than—or exactly four times. This is less than 200, and this is greater than 50, so I'm going to try three.

3 * 3 is 9, 3 * 5 is 15. Now let me subtract, and let's see, I can regroup again. I can take 10 from here and put it over here, so then that becomes 14. 14 - 9 is 5, 8 - 5 is 3, and then 100 - 100, or 1 - 1, is zero.

So I'm left with a remainder of 35, and that is a remainder because I can't divide 53 into it anymore. So I get this is equal to 13 remainder 35, and we're done.