9 is in the 1s place
5 is in the tens place
4 is in the hundreds place
4 is the number that we need to round up or down.
Take the number just before it.
If that number is greater than 5 round up.
If that number is less than 5 round down.
If that number is equal to five, which it is in this case, move to the next digit and do the same thing.
Since 9 is greater than 5 we need to round up
that means the 4 in the hundreds place rounds up to a 5.
3500