Rounding to the Nearest 10 Using Number Lines | 3-Digit Numbers | Lesson + Practice

Welcome to Math with Mr. J. In this video, I'm going to cover how to round three-digit numbers to the nearest 10 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 Victor drove 179 miles. About how many miles did he drive? Round 179 to the nearest 10. Now when we round to the nearest 10, we're looking for the closest 10. So 10, 20, 30, 40, 50, and so on. All of the numbers we get when we count up by 10s. Since we have more than 100 here, we have a three-digit number. Think 110, 120, 130, 140, 150, and so on. So we're still counting by 10s. The first thing that we need to do is figure out which two 10s 179 is between. I already have our number lines set up here, and we can see that 179 is between 170 and 180. Now let's find 179. 179 is right here. All we need to do now is find which 10 179 is closer to, 170 or 180. We can see that 179 is closer to 180. That's what 179 rounds to when we round to the nearest 10. So 179 rounds to 180. So going back to the original question, about how many miles did Victor drive? Victor drove about 180 miles. Remember, that word about tells us that we rounded, and the number isn't exact. And that's it. We rounded 179 to the nearest 10. Let's move on to number two, where we have 822. Let's round this to the nearest 10. First, we need to figure out which two 10s this is between. I have these laid out already. 820 and 830. Now we need to find 822. We have 820, 821, 822. So 822 is right here. So is 822 closer to 820 or 830? 822 is closer to 820. So 822 rounds to 820 when we round to the nearest 10. Moving on to number three, let's round 216 to the nearest 10. So which two 10s is 216 between? That's going to be 210 and 220. Now let's find 216. We have 210, 211, 212, 213, 214, 215, and 216. So right here. Is 216 closer to 210 or 220? This one can be tough to tell. So remember, it can be helpful to use the halfway point or middle, however you want to think about it, to make sure we round correctly. 215 is the halfway point between 210 and 220. So right here. Now 216 is to the right of 215, that halfway point. That means 216 is closer to 220. 216 rounds to 220. Lastly, let's move on to number four, where we need to round 645 to the nearest 10. 645 is between which two 10s? Well, 640 and 650. Now let's find 645. We have 640, 641, 642, 643, 644, and 645 is right here. 645 is exactly halfway between 640 and 650. So it's the same distance from both. So how do we round this? Remember, when a number is halfway between, we always round up to the greater number. So we need to round to the greater 10 here. 650. 645 rounds to 650. 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. We're rounding each of these to the nearest 10. For number one, 294 rounds to 290. For number two, 565 rounds to 570. For number three, 927 rounds to 930. For number four, 143 rounds to 140. For number five, 336 rounds to 340. And then lastly, for number six, 789 rounds to 790. So there you have it. There's how you round three-digit numbers to the nearest 10 using number lines. I hope that helped. Thanks so much for watching. Until next time, peace.