Rounding to the Nearest 10 Using Number Lines | 2-Digit Numbers | Lesson + Practice

Welcome to Math with Mr. J. In this video, I'm going to cover how to round two-digit numbers to the nearest ten 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 Olivia spent $23 at the store. About how much money did she spend? Round 23 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 tens. So the first thing we need to do here is figure out which two tens 23 is between. I already have our number line set up here, and we can see that 23 is between 20 and 30. 23 is greater than 20, but less than 30. Now let's find 23. 23 is right here. Now all we need to do is find which 10 23 is closer to. Is 23 closer to 20, or is 23 closer to 30? Well, we can see that 23 is closer to 20. 23 rounds to 20. So going back to the original question, about how much money did Olivia spend? Well, Olivia spent about $20 at the store. We use the word about to tell us that we rounded, and the number isn't exact. And that's it. We rounded 23 to the nearest 10. Now one thing I want to mention about number lines here is using the halfway point. So if we are unable to tell which number we are closer to, so which 10 we are closer to, we can use the halfway point to help us see that. So for example, the halfway point between 20 and 30 is 25. And let's actually split this in half. So these numbers to the left of 25 are closer to 20. They round to 20. So 21, 22, 23, and 24. And then the numbers to the right of 25 are closer to 30. They round to 30. So 26, 27, 28, and 29. Now you may be thinking, what about 25? Is that closer to 20 or 30? How would we round 25? We'll cover that later in the video. Let's move on to number two. And we need to round 58 to the nearest 10. First, we need to figure out which two 10s 58 is between. Well, I have these laid out already on our number line. 58 is between 50 and 60. Now we need to find 58. We have 50, 51, 52, 53, 54, 55, 56, 57, 58. So 58 is right here. So is 58 closer to 50 or 60? Well, 60. 58 rounds to 60. Next, for number three, we have 74. 74 is between which two 10s? Well, 70 and 80. Now let's find 74. We have 70, 71, 72, 73, 74. So 74 is right here. So is 74 closer to 70 or 80? 74 is closer to 70. 74 is close to halfway between 70 and 80, which halfway is right here at 75. But we can see that again, 74 is closer to 70. So 74 rounds to 70. Lastly, for number four, we have 35. First, we need to figure out the two 10s 35 is between. 35 is between 30 and 40. Then we need to find 35. We have 30, 31, 32, 33, 34, 35. So how do we round this? Is 35 closer to 30 or 40? 35 is exactly halfway between 30 and 40. So it's the same distance from both. When a number is halfway between, we always round up to the greater number. So we are going to round to the greater 10 here. That's 40. 35 rounds to 40. So again, when we have a number halfway between, we round up. Now, before we end here, I just want to say that rounding is a skill we use all the time in math and in everyday life. Rounding helps us get a close answer quickly. For example, about how much you spent at the store, about how many miles you traveled, or about how long you exercised. Rounding is used in all kinds of situations. 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, 82 rounds to 80. For number two, 45 rounds to 50. For number three, 21 rounds to 20. For number four, 14 rounds to 10. For number five, 77 rounds to 80. And then lastly, for number six, 98 rounds to 100. So there you have it. There's how to round to the nearest 10 using a number line. I hope that helped. Thanks so much for watching. Until next time, peace.