1.12 Round numbers
Are you ready?
We've seen how to break up, or partition, numbers , up to the thousands. Understanding how to do this will help us with our estimating.
Exploration
Enter a three digit number into the applet and drag the place value cards around to see what amount each digit represents.
The place value cards can be used to write the expanded form of the numbers.
Examples
Example 1
Fill in the boxes with the missing numbers.
698=⬚+⬚+8
We can use a place value table to write a number in expanded form.
Round numbers to the nearest 10
Sometimes we may need to solve problems by estimating. We can see if our number is closer to the ten before it, or after it. Let's see how we round our number to the nearest ten.
Examples
Example 2
Round 54 to the nearest ten.
To round a number to the nearest 10, plot the number on a number line to see which ten is closest to the number.
Rounding numbers in more ways
We can also round to the nearest hundred or thousand. Let's see how.
Examples
Example 3
Round 370 to the nearest hundred.
If you are rounding a number to the nearest 10, think about whether it is closer to the one above, or the one below. For example, 20 or 30.
If a number is exactly in the middle, round to the higher number.
This is the same for hundreds.