Sometimes I get asked the same type of stupid question by more than one person. I recently cycled along the Pacific Coast Highway in California for 135 miles. In 2003, I rode a 290-mile section. In 1998, 100 miles. Each time, prior to leaving on my trip, I was asked by more than one person, "Is it mostly downhill?"
Admittedly I ask dumb questions for fun, especially if the person I'm asking is uptight and needs to lighten up.
I still remember looking at the expression on the face of the National Park Service ranger at the toll booth as he was looking at the canoe strapped to the top of my van as I was about to drive through
Crater Lake National Park (for those that aren't aware, they don't allow private boats of any kind on Crater Lake). I couldn't help myself, so I asked the ranger where the nearest launch ramp was. I couldn't keep a straight face as he was explaining the regs to me, so half-way through his explanation, he figured out I was being a Smart-A.
Lastly, sometimes the person answering the question treats it like it's a stupid question when it isn't. When I was at Phantom Ranch in the bottom of the Grand Canyon a few years ago, I asked the girl working in the store, if they sold ice cream (I was looking for a ice cream cone from a soft ice cream machine). She explained all their supplies are brought in by burros and ice cream isn't possible to transport because it would melt. I said, "you sell ice don't you?" (they did) She rolled her eyes and let out an exaggerated sigh, getting ready to give me an education but I saved her the trouble and abruptly ended the conversation.
How stupid a question is depends on what side of the asking you're on.