Rounding to the nearest 1000
When rounding to the nearest 1000, the process is similar to rounding to the nearest 10 or 100, only this time we are checking which multiple of 1000 the number is closest to. Pupils first need to practise placing numbers with 4 or more digits correctly on a numberline marked in multiples of 1000, to identify the halfway numbers and recognise that they always have 5 hundreds. This leads to understanding that it is necessary to check the hundreds digit to see which multiple of 1000 it is closest to. The ones and tens digits are ignored, regardless of their size.
7 3 99 has less than 5 hundreds, meaning it is closer to 7000 than 8000, so it rounds down to 7000.
7 8 12 has more than 5 hundreds, meaning it is closer to 8000 than 7000, so it rounds up to 8000.
7 5 23 has 5 hundreds, meaning it is exactly halfway between multiples, so it also rounds up to the next multiple of 1000.
Summary
When rounding to the nearest 1000 , we check the hundreds digit, ignoring the tens and ones:
If the hundreds digit is less than 5, we round down to the previous multiple of 1000. The thousands digit stays the same and we replace any hundreds/tens/ones with zeroes.
If the hundreds digit is 5 or more, we round up to the next multiple of 1000. We add 1 to the thousands digit and we replace any hundreds/tens/ones with zeroes.
After rounding to 1000, the number will always end in at least three zeroes.