9243...

Is how many M&M's I had in a jar in my office (don't ask how I know that ;).  As a problem-solving exercise for PM's and Software Engineers, I'd ask job seekers (in this case RainMan) the obvious question, to which he replied, "9243"... yep, just like that.  No preamble, no qualifying questions regarding volume measures, whether I'd hidden a golf ball inside, nothing at all.  I was amazed and impressed at the fact that he knew the answer (frankly still am even though I was disappointed he didn't suggest it was "three minutes to Wapner.") ...right up until I asked him how he got it.
 
"I don't know", is what he said.
"What do you mean you 'don't know'?"
"It's 'right' though, isn't it?" he countered
"Yes, the answer is 9243, but how did you know?"
"Doesn't matter, just as long as I'm correct" was how he left it.

Do you want to work with someone like this or are you someone like this?

Working with someone like this is akin to getting in a car with a driver willing to take you to NYC, knows that it is your destination but doesn't have a map, doesn't ask any questions and can't give you any specifics on  how they're getting you there from where you are.

Do yourself and everyone you interview with a favor by asking good qualifying questions and then talking through your solutions.  It speaks to effective communication, will give them an idea of how you process information and how you'll work in a collaborative environment ...vinny