To find the sum of the smallest and the largest numbers that can be formed from the digits 4, 3, and 5:

1. Largest number: Arrange the digits in descending order:
   $543$.

2. Smallest number: Arrange the digits in ascending order:
   $345$.

Now, add them together: $543 + 345 = 888$

Thus, the sum of the smallest and the largest number is 888.

Would you like more details or have any further questions?

Here are 5 related questions to explore:

1. How many unique numbers can you form from three different digits?
2. What is the difference between the largest and smallest number formed by these digits?
3. If one digit is repeated, how does the result change?
4. How do permutations work when arranging digits?
5. What is the sum of the smallest and largest numbers formed by the digits 6, 7, and 8?

Tip: When forming the largest or smallest number from digits, always arrange them in descending or ascending order, respectively.