Rounding to the Nearest 100 Using Number Lines | Lesson + Practice

Welcome to Math with Mr. J. In this video, I'm going to cover how to round to the nearest hundred using number lines. We'll go through some examples together, and then I'll give you some practice problems that you can try on your own. Now, before we go into our examples, what does rounding even mean? When we round, we find a number that's close to the original number, but easier to work with. Basically, we're finding a nearby number that's simpler to use. Rounding helps us make quick estimates when we don't need an exact answer. Now, for our examples, we'll be using number lines to help us see how rounding works. Let's jump into number one, where we have James spent $283 at the grocery store. About how much money did he spend? Round to the nearest hundred. Now, when we round to the nearest hundred, we're looking for the closest hundred. So, 100, 200, 300, 400, 500, and so on. So, all of the numbers we get when counting up by hundreds. Now, the first thing that we need to do here is figure out which two hundreds 283 is between. I already have our number line set up here, so we can see that 283 is between 200 and 300. Now, we need to find 283. And for our number lines in this video, they will count up by tens. So, we will need to find roughly where 283 belongs. 283 is between 280 and 290. It's closer to 280, though. 283 is right around here. All we need to do now is find which hundred 283 is closer to, 200 or 300. We can see that 283 is closer to 300. That means 283 rounds to 300. Going back to the original question about how much money did James spend at the grocery store. James spent about $300. Remember, that word about tells us that we rounded and the number isn't exact. And that's it. We rounded 283 to the nearest hundred. Now, one thing I want to mention about using number lines to round is using the halfway point. So, if we are having a hard time telling which number we are closer to, so which number we are going to round to, we can use the halfway point to help us. For example, the halfway point between 200 and 300 is 250. And let's actually split this number line in half at that halfway point. Now, the numbers to the right of 250 are closer to 300. They round to 300. The numbers to the left of 250 are closer to 200. They round to 200. But what about 250? Is that closer to 200 or 300? How do we round 250 to the nearest hundred? We're actually going to cover that later in the video. Let's move on to our other examples. Moving on to number two, we have 847. Let's round to the nearest hundred. First, we need to figure out which two hundreds 847 is between. I have these laid out on our number line already. 847 is between 800 and 900. Now, we need to find 847. This is 800, 810, 820, 830, 840, 850. So 847 is between 840 and 850. It's going to be right around here. So is this closer to 800 or 900? This one can be tough to tell. 847 is pretty close to that halfway point, that halfway point of 850. And we can even split this number line in half. 847 is to the left of 850. That means it's closer to 800. It rounds to 800. So 847 rounds to 800. Let's move on to number three. We have 362. 362 is between 300 and 400. Now, we need to find 362. We have 300, 310, 320, 330, 340. The halfway point of 350 and then 360, 370. 362 is right around here between 360 and 370. Now, looking at this number line, is 362 closer to 300 or 400? Well, we know that the halfway point is 350 and we are to the right of that. So we are closer to 400 here. 362 rounds to 400. Moving on to number four, we have 629. So which two hundreds is 629 between? Well, 600 and 700. Now, we need to find 629. This is 600, 610, 620, and 630. 629 is between 620 and 630. It's almost at 630. So right about here. Now, is 629 closer to 600 or 700? 629 rounds to 600. And we can even use the halfway point, which is right here at 650. We are to the left of that. So again, we are closer to 600. Lastly, let's move on to number five. We have 450. 450 is between 400 and 500. Now, let's find 450. We have 400, 410, 420, 430, 440, and 450. So 450 is right here. 450 is exactly halfway between 400 and 500. So it's the same distance from both. So remember, when a number is halfway between, we always round up to the greater number. So we need to round to the greater hundred here. That's 500. 450 rounds to 500. So again, when a number is halfway between, we always round up. Now that we've gone through some examples together, it's time for you to try some practice problems on your own. So have paper and a pencil ready. Here are your practice problems. I'll give you three minutes, and then we will go over the answers. Feel free to pause if you need more time, or jump ahead to the answers whenever you are ready. Go ahead and start. Okay, so that was three minutes. Let's go over the answers. So here are our answers. For number one, 175 rounds to 200. For number two, 918 rounds to 900. For number three, 527 rounds to 500. For number four, 650 rounds to 700. For number five, 261 rounds to 300. And lastly, for number six, 349 rounds to 300. So there you have it. There's how to round to the nearest hundred using number lines. I hope that helped. Thanks so much for watching. Until next time, peace.