Here's a little fun aside for you, a problem I sat down with three adults a 10 year old and a 7 year old. The problem concerns a happy chap by the name of Eric the Sheep, which I sill summarize below (visit the site though there are some really interesting problems for kids).
Eric the sheep is lining up to be shorn before the hot summer ahead. There are fifty  sheep in front of him. Eric can't be bothered waiting in the queue properly, so he decides to sneak towards the front. Every time Eric passes two sheep, one sheep from the front of the line is taken in to be shorn. How many sheep will be shorn before Eric?
Well once we were close to the answer, and being a geek at heart, out came the ThinkPad and Python for a quick solution check ... so enjoy this.