How do you round 643 to the nearest hundred and nearest ten?

To round 643 to the nearest hundred, we look at the hundreds place digit, which is 6. Since the digit in the tens place, 4, is less than 5, we keep the hundreds place digit the same and change all following digits to zero. Therefore, 643 rounded to the nearest hundred is 600. To round 643 to the nearest ten, we look at the tens place digit, which is 4. Since 4 is less than 5, we keep the tens place digit the same and change all following digits to zero. Therefore, 643 rounded to the nearest ten is 640.