To round off a number to the nearest hundred, we check the last two digits of the number.
If the last two digits form a number less than 50, we round down the number to the nearest lower multiple of 100. 
If the last two digits form 50 or more than 50, we round up the number to the nearest higher multiple of 100.
To round off 30982 to the nearest hundred, our options are either 30900 or 31000.
Since 82 is greater than 50, 30982 is rounded off to 31000.