Subtraction of largest four digit number with smallest three digit number, rounded off to the nearest hundred is ______.

The correct option is C 9900
We know, largest four digit number = 9999 and smallest three digit number = 100
Upon subtracting, we get, 9999 - 100 = 9899

Now, we are asked to find the nearest hundreds of 9899.

9899 lies between 9800 and 9900.
The number formed by the last two digits of 9899 is 99.

If the last two digits form a number greater than or equal 50, then we round up the given number to the nearest multiple of 100 which is greater than the number.

$\because$ 99 > 50
$\therefore$ 899 will be rounded off as 900.
Hence, 9899 estimated to the nearest hundreds gives 9900.