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How to Round Numbers using a Rounding Rhyme and a Graphic Organizer

Updated on February 28, 2014

When you have a large number, sometimes it is useful to round it to make it easier to say, read, and remember. Being precise can get in the way when you just want a rough number, especially when the number is big. Most people don't care if there were 343,344 or 343,347 people at the event. Telling them that there were about 300,000 people is enough for them to understand the size of the crowd. Rounding numbers also helps when you are estimating.

How do you round numbers?

There are two steps in the process.

First, you need to think about how many places you want to round. If you are doing this for a class, your teacher will probably tell you.

Understand the Question

The first step is to figure out how far out you want to round. The farther to the left you are, the less precise your number is likely to be.

In this number: 123,456,789. The 9 is in the ones place, the 8 is in the tens place, the 7 is in the hundreds place, the 6 is in the thousands place, and so on. Please see the photo below for additional place values.

Round

Now that you know which number you are rounding, it is time to round. When we round, the number in the place you are rounding will either get to stay the same or go up a number. If the number immediately on the right is less than five, it will stay the same. If the number immediately on the right of it is five or greater, then it will get one number added to it. For example, if the number is a 2, it will get 1 added to it, so it is now a 3.

Graphic Organizer

Rounding Example

Let's say for purposes of this exercise, we will round to the hundred-millions. As you can see in the image above, the 1 is in the hundred-millions place.

Let's use a graphic organizer to make sure that we don't lose track of which numbers need our focus. Underline the number that is in the column that we need to round. This is the number that will either stay the same or go up one more. Then look to the number immediately on the right. Draw an arrow from it to the number you underlined to show that it is the number that will help you decide how to round the underlined number. You can ignore all of the other numbers for now.

Sometimes it is hard to remember which way the five should be rounded. Here's a rhyme to help you remember: "If it is bigger than four, it gets one more."

Here's how apply the rhyme to round.

Now we will look to the number immediately on the right of the 1. In this case, it is a 2. We apply the magic rhyme to the 2.

Rounding Rhyme

In this case, since the 2 is not bigger than 4, it is not strong enough to bump the 1 up. We leave the 1 as it is, and turn all the numbers to the right of the underlined number into zeroes.

Our number rounded to the millions is 100,000,000.

That's it, we did it!

Practice

Let's keep going for additional practice. Go ahead and round the same number to the ten millions, the millions, the hundred-thousands, the ten-thousands, the thousands, the hundreds and the tens place. Then come back to check your work.

Done already? Here are the answers.

Practice Answers

Rounding to Ten Millions

To round the number to the ten millions, we first find the digit that is in the ten-millions place. That is a 2 in our example. Be sure to underline it. Then, we look to the right of the 2 to see what number that is. It is a 3. Draw an arrow from the 3 to the 2. We apply the rhyme to the 3. "If it is bigger than four, it gets one more." Since the 3 is not bigger than 4, the 2 gets to stay as it is. Turn everything to the right of the underlined number into a zero. Our number rounded to the ten millions is 120,000,000.

Rounding to Millions Place

This is so much fun, let's keep going on to the millions place. We find the digit that is in the millions place. That is 3 in our example. Underline it. Then we look to the right of the 3 to see what number that is. That is a 4 in our example. Draw the arrow. We apply the rhyme to the 4. "If it is bigger than four, it gets one more." Since the 4 is not bigger than 4, the 3 gets to stay as it is. Everything to the right of the three turns into a zero. Our number rounded to the millions is 123,000,000.

Rounding to Hundred Thousands Place

Shall we keep going? Let's round to the hundred thousands place. We find the digit that is in the hundred thousands place. That is 4 in our example. Underline it. Then we look to the right of the 4 and find a 5 in our example. Draw the arrow. We apply the rhyme to the 5. "If it is bigger than four, it gets one more." In this case, we finally have a number that is bigger than 4. This means that it is strong enough to bump the four up. The 4 that is in the hundred thousands place gets one more, so change that into a five. Everything to the right of our new five turns into a zero. Our number rounded to the hundred thousands is 123,500,000.

Rounding to Ten Thousands Place

We're on a roll, let's keep going: Let's round to the ten- thousands place. We find the digit that is in the ten-thousands place. That is 5 in our example. Then we look to the right of the 5 and find a 6 in our example. Draw the arrow. We apply the rhyme to the 6. "If it is bigger than four, it gets one more." In this case, we have a number that is bigger than 4. The 5 that is in the ten-thousands place gets one more, so change the five to a six. Everything to the right of our new six becomes a zero. Our number rounded to the hundred thousands is 123,460,000.

Rounding to Thousands Place

We're so close; we might as well keep going. Let's round to the thousands place. We find the digit that is in the thousands place. That is 6 in our example. Underline it. Then we look to the right of the 6 and find a 7 in our example. We apply the rhyme to the 7. "If it is bigger than four, it gets one more." In this case, the seven is bigger than four. The 6 that is in the thousands place gets one more, and turns into a seven. Everything to the right of our new seven turns into a zero. Our number rounded to the hundred thousands is 123,457,000.

Rounding to Hundreds

Almost there! Let's round to the hundreds place. We find the digit that is in the hundreds place. That is 7 in our example. Underline it. Then we look to the right of the 7 and find an 8 in our example. Draw the arrow. We apply the rhyme to the 8. "If it is bigger than four, it gets one more." In this case, the eight is bigger than four. The 7 that is in the hundreds place gets one more. It turns into an 8, and everything to the right of the 8 turns into a 0. Our number rounded to the hundred thousands is 123,456,800.

Rounding to Tens

Last one. Almost there! Let's round to the tens place. We find the digit that is in the tens place. That is 8 in our example. Underline it. Then we look to the right of the 8 and find a 9 in our example. Draw the arrow. We can now apply the rhyme to the 9. "If it is bigger than four, it gets one more." In this case, the 9 is bigger than four. The 8 that is in the tens place gets one more. It turns into a 9, and everything to the right of the new 9 turns into a 0. Our number rounded to the hundred thousands is 123,456,790.

We cannot round to the ones place because we do not have any numbers after the ones place. If we had additional decimals, we would have been able to continue rounding the same way.

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    • Word Pools profile image
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      Word Pools 5 years ago from United States of America

      Thanks sarmack!

    • sarmack profile image

      Sarah 5 years ago from Washington

      Very neat!