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Year 4 Maths

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Rounding Numbers

About how many stars do you think are in the night sky? Sometimes it is easier to say about how many or how much something is instead of exactly how much. For instance, you might say that the night sky looks as if it contains 'about 4,000 stars', not '4,368 stars'. This is called rounding numbers. You round a number to show about how large it is.

night sky

In Year 3, we learnt about rounding numbers to the nearest ten. If the ones are less than five, you round down to the nearest ten. What is 54 rounded to the nearest ten? 50. If the ones are more than five, you round up to the nearest ten. What is 77 rounded to the nearest ten? 80. And do you remember the special rule for when a number is exactly between two numbers? When a number is exactly between two numbers, you round up to the greater number. So what is 35 rounded to the nearest ten? 40.

You can round a number to the nearest ten, hundred, thousand or hundred thousand. You round to these numbers in the same way. You can round to other numbers, too, but it usually makes it easier to round to numbers that have zeros as the last digits. To round a number to the nearest hundred, you make it into the hundred that is closest. Take the number 246, for example, which is between 200 and 300. It is closer to 200. So 246 rounded to the nearest hundred is 200.

number lines

The number 289 is also between 200 and 300, but it is closer to 300. So 289 rounded to the nearest hundred is 300.

Round 362 to the nearest hundred. 362 is between 300 and 400. It is closer to 400, so 362 rounded to the nearest hundred is 400. Now what is 8,257 rounded to the nearest thousand? 8,257 is between 8,000 and 9,000. It is closer to 8,000. So 8,257 rounded to the nearest thousand is 8,000.

You don't always round numbers to the highest place value, because it depends on how close to your number you want to be. For example, there are 7,652 books in Lucas's school library. What is 7,652 rounded to the nearest ten? 7,650. Now what if you round it to the nearest hundred? 7,700. What is it rounded to the nearest thousand? It’s 8,000.


This activity is adapted from pages 229-230 of What Your Year 4 Child Needs to Know, which can be purchased here.