So look at the number after the 5, if it's below a 5 then it will round down to 645000. So you can go up to 645,499 (assuming you only want integers and no decimals) At 644,xxx if the number is 5 or above then it rounds up, so that starts at 644,500
So the range is: 644,500-645,499 Or X is greater than or equal to 644500 and less than 645,500
They are all the numbers from 644,500 to 645,499 , including those two.
The numbers that round to 645,000 when rounded to the nearest thousand are those from 644,500 to 645,499. This includes any integer and decimal within that range. In mathematical terms, the range can be expressed as 644,500 ≤ x < 645,500.
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