Rounding 101 - Number Lines, Games and More

Why is Rounding So Important?

If you live in a state that uses math common core standards (3.NBT.1) or some variation, students are expected to know how to round whole numbers to the nearest 10 and 100, by the end of 3rd grade.

Even though rounding is a standard, I often feel like rounding is a “stepchild” math concept.  Sometimes we like to focus on the major players (ex. addition, subtraction, multiplication, division), and this very important skill gets put on the back burner.  I have been guilty too!

When students have a good grasp of rounding, they are capable of making reasonable estimates. Rounding and estimating are very useful in real life situations.  We use them to see if we have enough money when shopping or when trying to get somewhere on time.

But My Students Know that Rounding Rhyme

Over the years I used different strategies to teach rounding.  For example, I used the saying, “Five or higher add one more.  Four or less let it rest.”  I really enjoyed using that as a technique to round but then realized that my students really did not understand when or how to apply it.  After some research, I realized the importance of teaching rounding in a conceptual way.

Then What Can I Do?

Great question! There are many ways to teach rounding in a conceptual manner. You can use interactive number lines, engaging games, open-ended questions, and provide ample time for independent practice. Read below for more details.

1. Make and Use an Interactive Number Line

Have your students build an interactive number line from 0 - 100. First, color in the multiples of 10. Next have students work together to color code the numbers (ex. color stickers) that round to each multiple of 10.  Use the photo below as a model.

This helps create a clear visual and serves as an interactive model for students. I found that using different colored sticker dots is an easy way for students to color code an enlarged number line. However, if you don’t have stickers you can just draw your own dots with crayons or markers. Using the number line, students will determine where numbers 0 through 100 round. This is a great hands-on activity for whole group or small groups!

In order to get the most out of this activity, make sure that your students are able to verbally express how they rounded. I like to provide a sentence frame that students must use when speaking to one another. ( ___ rounds to ___ because it is ___ numbers away from ___ )

It is also a good idea to have students go all the way through the number line and record their findings.  See photo below.

2. Play Games

If you follow my blog then you know by now that I love using games to teach math concepts.  Games are a great way to keep students engaged and promote learning at the same time.  I choose two games that my kids loved to play and made 2 versions of each (Rounding to the nearest 10, Rounding to the nearest 100).

The first game is Rounding Face Off.  Students play against each other by simultaneously drawing a card from their separate piles and quickly matching it to a game board.  The player that makes the first correct match wins the round.

The second game is Rounding Concentration.  Students play against each other by taking turns flipping game cards to find a match. The player with the most matching pairs at the end wins. 

3. Ask Open-Ended Questions

What better way to see if kids really understand a topic than to ask open-ended questions?  I have found that when my kids have written responses to these types of questions I can easily see who “got” it and who did not. More importantly I can see if there are any misconceptions. 

One way is to ask students questions when they are using an open number line. For example, you can ask students to respond to questions like:

What patterns did you notice?

Explain how you got your answer.

Is the following true or false? How do you know?

Here are some examples of how I incorporated open-ended questions:

In this activity, students must use an open number line to solve the problem, but they also have to write a written explanation to explain their thinking.

In this activity, students must prove if a rounding statement is true or false.

4. Provide Time for Independent Practice

Students need lots and lots of practice!  Practice should include different ways to solve problems. I like to use different models and question types, so that students can visualize and explain their thinking in a variety of ways. When you are teaching rounding, it is also important to give problems that include 2 and 3 digit numbers that round to the nearest 10 or 100. Here are some examples of the different question types that are included in this activity packet.

Scaffold teaching the concept of rounding by using a number line and sentence frame. Students practice with a partner by rolling number cubes to get a random number and then use a sentence frame to help them explain their answers.

Next, they can practice independently with worksheets.  

Incorporate a high-yield teaching strategy, similarities and differences, by having students find examples and non-examples that round to a specific number.

Use models or open number lines to challenge students, and see their thought process.

If you would like the activities used in this blog post check it out here. Be sure to share ideas on how you teach rounding in your classroom (in the comments below).

If you also want to be able to review and assess your kids, check out the Rounding Bundle. 

It includes Rounding Flip and Go Cards and Rounding Exit Tickets.