When should you use multithreading? And would multi threading be beneficial if the different threads execute mutually independent tasks?

Question

This were the only two questions I couldn\'t answer in the interview I got rejected from last night.

Answer 1

You should use multithreading when you want to perform heavy operations without "blocking" the flow.
Example in UIs where you do a heavy processing in a background thread but the UI is still active.

If the threads execute mutually exclusive tasks it is the best since there is no overhead for synchronization among threads needed