What number is greater than 535 but rounded to the nearest 100 is 500?
which one?

523 535 545 550

545

This is because in rounding, numbers are rounded up when they are past the halfway mark, but down when they are below the halfway mark. If the number is exactly the halfway point, then it is also usually rounded up.
In this case, the halfway point is 550. 545 is less than 550, so if it is rounded to the nearest 100, it is rounded down to 500.

545 because the 45 is more than 35 and the answer is still 500 when rounded off