Rounding numbers

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When you round a number, you switch to a nearby number that's easier to work with. For example, if Krista drove 104 miles this morning, you could say that's about 100 miles. You can use rounding to

estimate

answers to math problems.

How do you round?

When you round, you move to the nearest major number. For example, you might round a number to the nearest ten, hundred, or thousand.

Let's try it! To start, let's round 47 to the nearest ten. You can look at a number line to see that 50 is the nearest ten.

, indigo CLOSED point,

tick mark,

But you can also round without looking at a number line. Just follow these steps:

First, find the digit in the
place
you are rounding to.
Look at the digit one place to the right.
If the digit is less than 5, round down. If the digit is 5 or greater, round up.

Let's go back and try this with 47. First, find the digit in the tens place.

Now, look one place to the right.

Since 7 is greater than 5, round up.

47 → 50

So, 47 rounded to the nearest ten is

50.

Another example

Next, let's try rounding 382 to the nearest ten.

First, find the digit in the tens place.

382

Now, look one place to the right.

382

Since the digit 2 is less than 5, round down.

382 → 380

382 rounded to the nearest ten is

380.

Rounding with larger numbers

Next, let's try rounding 1,251 to the nearest hundred.

First, find the digit in the hundreds place.

1,251

Now, look one place to the right.

1,251

Since the digit 5 is 5 or greater, round up.

1,251 → 1,300

1,251 rounded to the nearest hundred is 1,300.

Another example

You can round with real-world numbers, too! For example, the population of New York City in the year 1900 was 3,437,202 people. Let's round that to the nearest hundred thousand.

First, find the digit in the hundred-thousands place.

3,437,202

Now, look one place to the right.

3,437,202

Since the digit is less than 5, round down.

3,437,202 → 3,400,000

3,437,202 rounded to the nearest hundred thousand is 3,400,000.