It is: 3450
145 is the least number that can be rounded to 150.
Any number such that 3535 < x ≤ 3545.
3500
The nearest hundred to 3500 is 3500 itself. When rounding to the nearest hundred, you look at the digit in the tens place. If it is 5 or greater, you round up; if it is less than 5, you round down. In this case, the digit in the tens place is 5, so you would round up to 3500.
The least number that can be rounded to 400 (to the nearest 400) is 200.
500,000 is the least whole number that can be rounded to the nearest millions.
3500
3500
3500
3500
3500