12,781 rounded to the nearest hundred?

12800
When rounding a number to the nearest hundred you look at the number in the hundreds place, in this case it the digit 7. To decide if you will be rounding it up to 8, or leaving it at 7 you need to look at the digit to the right of it, in this case there is an 8 in the tens place. It that digit is a 5 or greater you round up, if that digit is a 4 or less you leave it as it is. Since the digit is 8 and that is a five or greater you will round up to place an 8 in the hundreds place. The places to the right of the number place you are rounding become zeros.