What is the sum of the smallest and the largest possible numbers that can be formed from the digits 1, 2 and 3 if they are all to be used exactly once?

1. 444

The correct option is A 444
To find the largest number that can be formed from the digits 1, 2 and 3, we arrange the digits in descending order.

$\therefore$ The largest number using the given digits is 321.

We follow the reverse process for finding the smallest possible number.

$\therefore$ The smallest number using the digits is 123.

$123\underset{–}{321}+\underset{–}{444}$

$\therefore$ The required sum is 444.