Math riddles?

[Apache]

So, I've noticed there are no more math puzzles on this site (and that this is the only real active site section apart from fm)

since i'm a great fan of math puzzles, i could post some if ppl want this. it would be math questions, that aren't too hard, so they could be solved by most people, but they require some logical thought process.
i would post one each week or each 2 weeks, depending on activity. i could also make a ranking who solved most puzzles.

is this something you want/would do?

[louiswill]

Please post some unique solution puzzle of nth order homogenous linear ordinary differential equation, because those give me real headache this quarter I really want to see how other people react to wronskian.

[Orpz]

I would love to participate