Design Interview questions

1.) You are adding 8 10-bit numbers. How many bits do you need for the result?
2.) You are adding two 2's-complement numbers together. One is 8 bits, the other is 4 bits. How do you handle the fact that the two numbers are not the same width?
3.) You have a free running clock. How would you design a divide by 3 circuit.

4.) Describe the design of a FIFO circuit.
5.) Describe the design of a bus arbiter circuit.