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1.05 Round numbers

Lesson

Are you ready?

Can you  round 3 or 4 digit numbers  ?

Examples

Example 1

Round 7521 to the nearest thousand.

Worked Solution
Create a strategy

Use a number line starting with the thousands value and ending with the next thousands value.

Apply the idea

Start the number line at 7000 and end with 8000. Plot 7521.

70007100720073007400750076007700780079008000

7521 is closer to 8000 than 7000.

The rounded value is 8000.

Idea summary

When rounding a number to the nearest thousands:

  • Use a number line to check if it is closer to the thousands above, or the thousands below the number.

  • If a number is exactly in the middle, round to the higher number.

Round numbers up to 5 digits

Sometimes we only need an approximation of our number, rather than the exact value. We work out which number it is closest to, and we can do this on a number line, or using the rule for rounding. Let's see how to do both of these things in this video.

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Examples

Example 2

Round 96\,501 to the nearest thousand.

Worked Solution
Create a strategy

Use a number line starting with the thousands value and ending with the next thousands value.

Apply the idea

Start the number line with 96\,000 and end with 97\,000.

9600096100962009630096400965009660096700968009690097000

96\,501 is higher than 96\,500 and is closer to 97\,000.

The rounded value is 97\,000.

Idea summary

It doesn't matter how many places our numbers have, when we round the number, we need to know what we are rounding it to. If we round 130 to the nearest hundred, we will get a different answer than if we round it to the nearest ten.

Outcomes

MA2-5NA

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers

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