Well, honey, 331 rounded to the nearest 100 is 300. It's not rocket science, just drop those pesky little digits and call it a day. Math doesn't have to be a headache, darling.
When rounding 331 to the nearest 100, you would look at the digit in the tens place, which is 3. Since 3 is less than 5, you would round down. Therefore, 331 rounded to the nearest 100 is 300.