Extra credit on a test: Follow Up

The question I decided on is this: "Portland is the largest city in Maine. What is its population, to with 10,000 people?"

I'll post the answer when everyone has taken the test. Hint: it's pretty small for a state's largest city.

Update 3/30/08
The test is over. The answer is about 64,000. I got answers ranging anywhere from 8,000 to 4 million (nearly four times the population of the entire state of Maine). It's kind of sad and amusing at the same time when you realize that so many kids have such little concept of anything like that.

Extra credit on a test

I don't give many extra credit assignments, but I do like to put a bonus question on a test, worth a few extra points added to the overall score. These are sometimes questions about physics or astronomy ("What star is closest to us besides the sun?"), the school ("What year did the science building open?"), or other random things ("At what point in his life did your teacher start playing the bagpipes?"). Little fun things that they either know or can make a reasonable guess.

I'm giving a test tomorrow in my Honors Physics classes, and I'm trying to think of a good question to use as a bonus. Any ideas?

P.S. - Alpha Centauri, 1995-1996 school year, college or age 18