How did they even graduate from high school? Completely Clueless Week at College Insurrection.
As someone who is relatively young in business but now occasionally asked to interview possible new hires, I have developed a list of general information questions which I like to use. Math, history, religion, scope of reading, current events, art, etc. After all, unless somebody is a genius in our field, you really want to hire people you want to be around and to work with, and secondarily people who you think can help make money because they are young and that can be hard to predict.
If they don't help you make money you can just let them go, but they at least have been good company for a while.