When rounding numbers up or down, you need to look at the number in the place to the right of the place you are rounding to.
You have been asked to round to the nearest hundred (3rd place from the right)
Look one place to the right of the hundred place (the ten's place in this instance). If it is 4 or less, you will leave the hundred's digit as is and fill in the tens and ones places with a zero (this is called rounding down).
If it is 5 or higher, you will "round up" the digit in the hundred's place to the next hundred.
348 has a 4 in the tens place - so we will "round down" by leaving the hundred digit and placing zeros in the tens and ones. (300)
452 rounds up to 500 (because of the 5 in the tens place)
325 rounds down...
423 rounds down...
351 rounds up to ... 400! We found our answer
445 rounds down...
