Teaching Rounding with a Number Line

Teaching rounding with a number line helps kids understand what it’s all about. The tactile experience lets them explore base-ten place value in a meaningful way. Before you ask your students to look at the number next door, break out some number lines.

Ms. Sneed Likes Teaching Rounding with a Number Line

Our favorite fourth grade teacher sat at the side table with her student teacher. “Today, we’ll continue planning our place value unit,” Ms. Sneed said. “It’s time to teach our kids how to round multi-digit numbers.”

“Ah,” said Mr. Grow. “I remember that trick. Just look at the number to the right. If it’s zero through four, round down. But for five through nine, round up.”

“Actually, we won’t be using that method. Instead, we’ll be teaching rounding with a number line.”

Mr. Grow looked a little perplexed but said nothing. When it came to fourth grade math, he knew there was always a method to Ms. Sneed’s madness.

Begin Teaching Rounding with a Number Line

As usual, Ms. Sneed opened her laptop. With a few clicks, she found what she was looking for.

“On the first day of teaching rounding,” she began, “we’ll only look at three-digit numbers.”

Turning the laptop so Mr. Grow could see better, she continued. “These anchor charts demonstrate how to round 357 to the nearest 10, 100, and 1000.”

Mr. Grow took a closer look. “I’m beginning to see why this is a good first step. When they round to the nearest ten, for example, they actually count by tens to find the two multiples that 357 comes between: 350 and 360. Then they plot 357 and find which of those numbers it’s around. Clever!”

With a smile, Ms. Sneed responded. “Yes, then they count by hundreds to round to the nearest hundred and by thousands to round to the nearest thousand. If you consider what’s going on in their heads during all of this, you’ll understand the power of the process.”

Her mentee nodded. “I’m beginning to see a big difference between the way I was taught and how you do it. You teach for understanding.”

Begin teaching rounding with number lines on anchor charts.
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Support Early Experiences with Number Lines

Now Ms. Sneed scrolled to a set of worksheets. “As our kids venture out on their own,” she said, “we’ll limit their experiences. For example, after teaching rounding to the nearest ten, kids will only work with tens. Then we’ll move on to hundreds, and then thousands.”

“So we’re taking it slow,” said Mr. Grow.

“Yes. Although we’ll move along at a pretty good clip time-wise, instruction is broken into bite-sized pieces that are easy to swallow. As I always say, scaffold, scaffold, scaffold.”

When teaching rounding with number lines, give kids supported worksheets.

Next, Move to Bigger Numbers

Once again, Ms. Sneed scrolled to another page. “Now we’ll move on to teaching rounding of larger numbers. Fourth grade students must work with digits to the hundred thousands.”

“I see a big jump,” the student teacher said. “On this anchor chart, kids see how one number is rounded to four different place values.”

“Correct. At this point, they need to move between tens, hundreds, thousands, and ten thousands.”

Now that you've finished teaching rounding with number lines with smaller numbers, move to bigger ones.

Give More Practice with Number Lines

Ms. Sneed sighed. “Here’s where teaching rounding gets tough. You can anticipate some students needing a lot of support. In addition to number lines, you’ll need to pull struggling learners to the side table for help.”

She displayed the worksheets kids would do next. “As you can see, students must fill in the rectangles with the multiples that fall on either side of the number. Then they need to plot it and determine which is closer.”

Continue to support students with number lines as they begin to round to the nearest 10, 100, 1000 and beyond.

Continue Teaching Rounding with a Number Line Option

“Our students will fall into two camps now: a few who can easily round and many who cannot.”

She scrolled to some blank templates. “We’ll make copies of these number line pages to support kids who are still trying to grasp rounding. As a matter of fact, at this grade level, I believe that kids should even be allowed to use them on tests.”

When teaching rounding, keep blank number lines handy for remediation.

After Lots of Practice, Introduce the Trick

Ms. Sneed sat back in her chair and smiled. “Okay, I’ll admit it. After teaching rounding with number lines – and lots of practice – I do show kids the trick.”

She displayed another anchor chart on the screen of her laptop.

Mr. Grow chuckled and added, “But I see you introduce it in a conceptual way.”

“True, but after this, kids do begin talking about the number next door. And that’s okay. Because they already have understanding of the concept behind it.”

After teaching rounding with number lines, you can finally teach kids the trick about looking next door.

Give Even More Practice

Displaying two more worksheets, Ms. Sneed said, “Before the final assessment, our students need more practice. And many more of them will be ready to round without number lines. Some kids, however, will be ready for an even bigger challenge. These differentiated sheets let them work with numbers in the millions period. Even though they’re only rounding to the nearest ten thousand, they’ll show that they can’t be distracted by so many digits.”

After lots of conceptual exploration, kids are finally ready for simple worksheets.

Enjoy Teaching Place Value

Mr. Grow looked through his notes. “So, our place value unit addresses the value of each digit; reading multi-digit numbers; writing them in standard form, words, and expanded form; and rounding. Anything else?”

“Just one more concept: ordering and comparing numbers. But usually, our kids come to fourth grade with a decent grasp of this. So we’ll just play games.”

It was Mr. Grow’s turn to smile. “I really like this unit. It will be fun to teach.”

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