The problems presented to you, in an interview, will be directly related to what the task in front of you should you get the job... If the problem cannot be solved, within the time specified, then possibly you're not the man for the job..
When I interview staff, I kinda know within several minutes if the candidate is right for the job... I know that on site training will be needed for ANY candidate even if they know a great deal.. If someone has done their homework, then they will come across more confident. Not cocky , but a more relaxed confidence.. Showing interest in the job always goes down well. Flattery ( but not over the top ) also helps... I want someone who will promote our products as if they were his own, even if they are only playing bit parts in the products I sell...