Rounding on the Number Line 

Rounding on the number line is one of those tricky skills that students in grade 2 and up often struggle with.  The task seems so easy because we aren’t asking our students to solve any complex equations or problem solve.  We are simply asking them to estimate, right?  If we ask them to round to the nearest tens, what we are really saying is “can you use your number sense to tell me which multiple of ten this number is closest to ?”    It’s important for students to understand why we are asking them to complete that rounding to the nearest tens and hundreds worksheet.  

Estimation is a skill that adults use on a regular basis when preparing food, planning events, budgeting, etc.  We are using our deeper understanding of how numbers work (number sense) to determine about how much we have.  Knowing about how much we have or need allows us to quickly do mental calculations.  We are able to interpret data faster and check our work for reasonableness (does it make sense).  

Rounding to the Nearest Tens Real World Example 

One example I like to have my students think about is planning for a birthday party.  They may have sent out twenty-five invites and 17 people actually RSVP.  When planning for the party, do we want to prepare exactly 17 bags?  This is a great math talk question because students will give several answers and it allows students to question each other’s thinking. Once you have engaged your students in this task you need to make sure they understand which numbers we think are easiest to add.  That would be the ones that end in zeros and ones that we commonly use like those that end in five.  

Rounding on the number line is a form of estimation.  It is important to begin rounding by using a number line to ensure that students have a conceptual understanding of rounding.  This deeper understanding will allow them to apply their knowledge when problem solving both in the classroom and in the real world. Now that we know why rounding on the number line is a must, let’s take a look at the steps.

How Do You Round to the Nearest Tens?

The first step in rounding on the number line is to actually create the number line.  Students will need to know how to skip count by the number they are rounding to past 100.  To practice this skill I like to have my students skip-count around the room starting at different numbers.  For example, I might say, “skip-count by tens and let’s start at 90”.  This way they understand that number lines don’t always start at zero and they actually do go past 100.  Once you have practiced this skill students will easily apply it when rounding on the number line.

Now Let’s Round on the Number Line

For this practice of rounding to the nearest tens let’s use the number 53.  First, students should label their number line by skip-counting by tens, it should include the range from 50 to 60.  Remember that where they start and stop isn’t as important as having the correct increments of 10.  Next, students should be able to identify which two multiples of ten are around the number 53 (50 and 60).  Then, have students determine and mark the halfway point between 50 and 60, which is 55.  After that, have them mark where the number 53 should go in relation to the halfway point.  Here is where you get to teach them the agreed upon conventions of rounding.  If the number is at the halfway point or greater we round up. If the number is less than half they round down. The final step is for students to determine if they should round up or round down. 

So let’s review the 5 easy steps to rounding on the number line:

1. Label your number line by skip-counting by 10; 100; 1,00; etc
2. Decide which two tens your number is between
3. Label the halfway point
4. Place your number on the number line
5. Round up or round down

Rounding to hundreds

Now that you’ve taught rounding on the number line to the nearest tens, it should be a breeze to teach rounding to the hundreds.  You can use the same five steps above, but students should skip-count by hundreds (this can also be practiced beforehand).  Certain students may also have trouble determining the halfway point.  If need be, use a number line to show them that half of 100 is fifty. 

Once students have a conceptual understanding of what it means to round, then you can introduce those cute anchor charts that use chants such as this free one. Introducing these too early in your students’ rounding journey could lead to them knowing how to round correctly, but not understanding when to round or why they should round.  When they get to problem solving that requires rounding, but doesn’t explicitly say round to the nearest tens or round to the nearest hundreds, there will be confusion.

Practice rounding on the number line

Now that you know the easy steps to teaching rounding on the number line you are ready for your students practice.  You can click here to get a 3rd grade rounding worksheets bundle that includes lessons slides, practice slides, self-checking practice and digital mazes.  If you would like individual rounding to the nearest tens and hundreds worksheets (digital) those are also available.  Remember, to have your students practice skip counting on a regular basis to make rounding on the number line easier.  This will help build their number sense and prepare them for estimation problem solving. If your scholar is still having trouble understanding and you’re ready to call in a professional click here for more details.